Cells were discovered byRobert Hooke in 1665, who named them after their resemblance tocells in amonastery.Cell theory, developed in 1839 byMatthias Jakob Schleiden andTheodor Schwann, states that all organisms are composed of one or more cells, that cells are the fundamental unit of structure and function in all organisms, and that all cells come from pre-existing cells.
Most prokaryotes are the smallest of all organisms, ranging from 0.5 to 2.0 μm in diameter.[12] The largest bacterium known,Thiomargarita magnifica, is visible to the naked eye with an average length of1 cm, but can be as much as2 cm[13][14]
Bacteria are enclosed in acell envelope, that protects the interior from the exterior.[15] It generally consists of aplasma membrane covered by acell wall which, for some bacteria, is covered by a third gelatinous layer called abacterial capsule. The capsule may bepolysaccharide as inpneumococci,meningococci orpolypeptide asBacillus anthracis orhyaluronic acid as instreptococci.Mycoplasma only possess the cell membrane.[16] The cell envelope gives rigidity to the cell and separates the interior of the cell from its environment, serving as a protective mechanical and chemical filter.[17] The cell wall consists ofpeptidoglycan and acts as an additional barrier against exterior forces.[18][17] The cell wall acts to protect the cell mechanically and chemically from its environment, and is an additional layer of protection to the cell membrane. It also prevents the cell from expanding and bursting (cytolysis) fromosmotic pressure due to ahypotonic environment.[19]
Cell-surface appendages can includeflagella, andpili, protein structures that facilitate movement and communication between cells.[34] The flagellum stretches from the cytoplasm through the cell membrane and extrudes through the cell wall.[35]Fimbriae are short attachment pili, the other type of pilus is the longerconjugative type.[36] Fimbriae are formed of anantigenic protein calledpilin, and are responsible for the attachment of bacteria to specific receptors on host cells.[37]
Archaea are enclosed in a cell envelope consisting of a plasma membrane and a cell wall.An exception to this is theThermoplasma that only has the cell membrane.[16] The cell membranes of archaea are unique, consisting ofether-linked lipids. Theprokaryotic cytoskeleton has homologues of eukaryoticactin andtubulin.[27] A unique form of metabolism in the archaean ismethanogenesis. Theircell-surface appendage equivalent of the flagella is the differently structured and uniquearchaellum.[38][36] The DNA is contained in a circular chromosome in direct contact with the cytoplasm, in a region known as the nucleoid. Ribosomes are also found freely in the cytoplasm, or attached to the cell membrane where DNA processing takes place.[23][39]
The archaea are noted for theirextremophile species, and many are selectively evolved to thrive in extreme heat, cold, acidic, alkaline, or high salt conditions.[40] There are no known archaean pathogens.[41]
Eukaryotes can be single-celled, as indiatoms (microscopic algae), or multicellular, as inanimals,plants, mostfungi, and somealgae.[42]Multicellular organisms are made up of many differenttypes of cell known overall assomatic cells.[43] Eukaryotes are distinguished by the presence of a membrane-boundnucleus.[44] The nucleus gives the eukaryote its name, which means "true nut" or "true kernel", where "nut" means the nucleus.[45] A eukaryotic cell can be 2 to 1000 times larger in diameter than a typical prokaryotic cell.[46]
Eukaryotic cells have acell membrane that surrounds a gel-likecytoplasm. The cytoplasm contains thecytoskeleton, the cell nucleus, the endoplasmic reticulum, ribosomes, the Golgi apparatus, mitochondria,lysosomes,peroxisomes,endosomes, vacuoles and vesicles, and may have a cell wall, chloroplasts,vaults, andcell-surface appendages. There are many cell variations among the different eukaryote groups.
The membranes of most of the organelles including the cell membrane are sometimes referred to as theendomembrane system.[47] All of these membranes are involved in thesecretory andendocytic pathways, modifying, packaging, and transporting proteins and lipids to and from the trans-Golgi network.[48] Inmammalian cells, endocytosis includes early, late, and recyclingendosomes.[48]
Most distinct cell types arise from a singletotipotent cell, called azygote, thatdifferentiates into hundreds of different cell types during the course ofdevelopment. Differentiation of cells is driven by different environmental cues (such as cell–cell interaction) and intrinsic differences (such as those caused by the uneven distribution ofmolecules duringdivision).[49]
Eukaryotic cell types include those that make upanimals,plants,fungi,algae, andprotists. All of which have many different species and cell differences.
All the cells in an animal body develop from onetotipotentdiploid cell called azygote. During theembryonic development of ananimal, the cellsdifferentiate into the specialisedtissues andorgans of the organism. Different groups of cells differentiate from thegerm layers. Thesponge has only one layer. Some other animals known asdiploblasts have two germ layers theectoderm, and theendoderm. More advanced animals have an extra layer, the middlemesodermal layer, and are known astriploblastic. Triploblastic animals make up the largeclade ofBilateria. Differentiation results in structural or functional changes tostem cells, andprogenitor cells. There are an estimated 200 differentcell types in the human body. The estimatedcell count in a typical adult human body is around 30 trillion cells, 36 trillion in an adult male, and 28 trillion in a female.[50]
Structure
An animal cell has acell membrane that surrounds a gel-likecytoplasm. The cytoplasm contains thecytoskeleton, the cell nucleus, the endoplasmic reticulum, ribosomes, the Golgi apparatus, mitochondria,lysosomes,peroxisomes,endosomes, vacuoles and vesicles, andvaults. An animal cell structure, as other eukaryotes, includes anendomembrane system encompassing all the membranes of the organelles and the cell membrane, excluding the mitochondria.The whole system cooperates in the modification, packaging, and transport of proteins and lipids.[47]
Diagram of cell membrane detailing membrane proteins
Thecell membrane, or plasma membrane, is aselectively permeablemembrane as an outer boundary of the cell that encloses the cytoplasm.[51] The membrane serves to separate and protect a cell from its surrounding environment and is made mostly from alipid bilayer ofphospholipids, which areamphiphilic (partlyhydrophobic and partlyhydrophilic). It has been best described in thefluid mosaic model.[52] Embedded within the cell membrane is amacromolecular structure called theporosome the universal secretory portal in cells and a variety ofprotein molecules that act as channels and pumps that move different molecules into and out of the cell.[23] The membrane is semi-permeable, and selectively permeable, in that it can either let a substance (molecule orion) pass through freely, to a limited extent or not at all.[53]Cell surface receptors embedded in the membrane allow cells to detect external signaling molecules such ashormones.[54]
Underlying, and attached to the cell membrane is thecell cortex, the outermost part of the actin cytoskeleton.[55]
Cytoplasm
The cell membrane encloses thecytoplasm of the cell that surrounds all of the cell's organelles.[56][57] It is made up of two main components, theprotein filaments that make up thecytoskeleton, and thecytosol.[56][57] The network of filaments and microtubules of the cytoskeleton gives shape and support to the cell, and has a part in organising the cell components. The cytosol is the main site ofprotein synthesis, anddegradation.[57]
The cytosol is a gel-like substance made up of water, ions, and non-essential biomolecules. The acidity (pH) of the cytosol is near neutral, and transporters in the cell membrane regulate this. Different proteins in the cytoplasm operate optimally at different pHs.[58] The cytosol forms30%–50% of the cell's volume.[59]
Cytoskeleton
Thecytoskeleton acts to organize and maintain the cell's shape; anchors organelles in place; helps duringendocytosis, and in the uptake of external materials by a cell.The cytoskeleton is composed ofmicrotubules,intermediate filaments andmicrofilaments. There are a great number of proteins associated with them, each controlling a cell's structure by directing, bundling, and aligning filaments. The outermost part of the cytoskeleton is thecell cortex, oractin cortex, a thin layer of cross-linkedactomyosins.[55] Its thickness varies with cell type and physiology.[55] It directs the transport through theER and theGolgi apparatus.[60] The cytoskeleton in the animal cell also plays a part incytokinesis, in the formation of thespindle apparatus duringcell division, the separation of daughter cells.
Organelles arecompartments of the cell that are specialized for carrying out one or more functions, analogous to theorgans, such as the heart, and lungs.[23] There are several types of organelles held in the cytoplasm. Most organelles are membrane-bounded, and vary in size and number based on the growth of the host cell.[61] Organelles include the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, vesicles, and vacuoles.[62] Non membrane-bounded organelles include the centrosome, and typically the ribosome.[62]
Thecell nucleus is the largest organelle in the animal cell.[50] It houses the cell'schromosomes, and is the place where almost allDNA replication andRNA synthesis (transcription) occur. The nucleus is spherical and separated from the cytoplasm by a double-membranednuclear envelope. A space between the membranes is called the perinuclear space. The nuclear envelope isolates and protects a cell's DNA from various molecules that could accidentally damage its structure or interfere with its processing. During processing,DNA istranscribed, or copied into a specialRNA, calledmessenger RNA (mRNA). This mRNA is then transported out of the nucleus, where it is translated into a specific protein molecule. Thenucleolus is a specialized region within the nucleus where ribosome subunits are assembled.[23] Cells use DNA for their long-term information storage that isencoded in itsDNA sequence.[23] RNA is used for information transport (e.g.,mRNA) andenzymatic functions (e.g.,ribosomal RNA).Transfer RNA (tRNA) molecules are used to add amino acids during proteintranslation.[63]
Theendoplasmic reticulum (ER) is a transport network for molecules targeted for certain modifications and specific destinations, as compared to molecules that float freely in the cytoplasm. The ER has two forms: therough endoplasmic reticulum (RER), which hasribosomes on its surface that secrete proteins into the ER, and thesmooth endoplasmic reticulum (SER), which lacks ribosomes.[23] The smooth ER plays a role in calcium sequestration and release, and helps in synthesis oflipid.[66]
Golgi apparatus
TheGolgi apparatus processes and packagesproteins, andlipids, that are synthesized by the cell. It is organized as a stack of plate-like structures known ascisternae.[67]
Mitochondria
Mitochondria generate energy for the cell. Mitochondria are self-replicating double membrane-bound organelles that occur in various numbers, shapes, and sizes in the cytoplasm of the cell.[23]Respiration occurs in the cell mitochondria, which generate the cell's energy byoxidative phosphorylation, usingoxygen to release energy stored in cellular nutrients (typically pertaining toglucose) to generateATP (aerobic respiration).[68] Mitochondria multiply bybinary fission.[69] Mitochondria have their own DNA (mitochondrial DNA).[70] The mitochondrial genome is a circular DNA molecule distinct from nuclear DNA. Although the mitochondrial DNA is very small compared to nuclear chromosomes,[23] it codes for 13 proteins involved in mitochondrial energy production and specific tRNAs.[71]
Lysosomes
Lysosomes contain over 60 differenthydrolytic enzymes.[72] They digest excess or worn-out organelles, food particles, and engulfedviruses orbacteria. Lysosomes are optimally active in an acidic environment. The cell could not house these destructive enzymes if they were not contained in a membrane-bound system.[23][73]
Peroxisomes
Peroxisomes, aremicrobodies bounded by a single membrane. A peroxisome has no DNA or ribosomes and the proteins that it needs are encoded in the nucleus, and selectively imported from the cytosol. Some proteins enter via the endomembrane reticulum.[74] They have enzymes that rid the cell of toxicperoxides. The enzymatic content of the peroxisomes varies widely across the species, as it can in an individual organism.[75][74] The peroxisomes in animal cells are concentrated in theliver cells andadipocytes.[75]
Vacuoles
Vacuoles sequester waste products. Some cells, most notablyAmoeba, have contractile vacuoles, which can pump water out of the cell if there is too much water.[76]
Aribosome is a large complex ofRNA andprotein molecules often considered as anon-membrane-bound organelle.[23] They each consist of two subunits, one larger than the other, and act as an assembly line where RNA from the nucleus is used to synthesise proteins from amino acids. Ribosomes can be found either floating freely or bound to a membrane of the rough endoplasmatic reticulum.[79]
Vaults
Avault is a large ribonuclear protein particle, anon-membrane-bound organelle, three times the size of a ribosome but with only three proteins in contrast to the near hundred in the ribosome.[80] Most human cells have around 10,000 vaults, and in some types ofimmune cell there may be up to 100,000.Macrophages have the greatest number of vaults of any human cell.[81] Vaults are largely overlooked because their functions are purely speculative. They may play a role in transport from the nucleus to the cytoplasm, and may serve as scaffolds for signal transduction proteins. They are present in normal tissues, and more so in secretory and excretory epithelial cells.[80][81]
Some types of specialised cell are localised to a particular animal group.Vertebrates for example have specialised, structurally changed cells includingmuscle cells. The cell membrane of askeletal muscle cell or of acardiac muscle cell is termed thesarcolemma.[82] And the cytoplasm is termed thesarcoplasm. Skeletal muscle cells also becomemultinucleated. Populations of animal groupsevolve to become distinct species, where sexual reproduction is isolated. The manyspecies of vertebrates for example have other unique characteristics by way of additional specialised cells. In some species ofelectric fish for example modified muscle cells or nerve cells have specialised to becomeelecterocytes capable of creating and storing electrical energy for future release, as in stunning prey, or use inelectrolocation.[83] These are large flat cells in theelectric eel, andelectric ray in which thousands are stacked into anelectric organ comparable to avoltaic pile.[84]
Many animal cells areciliated and most cells except red blood cells haveprimary cilia. Primary cilia play important roles inchemosensation andmechanosensation.[85][86] Each cilium may be "viewed as a sensory cellularantennae that coordinates a large number of cellular signaling pathways, sometimes coupling the signaling to ciliary motility or alternatively to cell division and differentiation."[87] The cilia in other cells are motile organelles, and in therespiratory epithelium play an important role in themovement of mucus. In the reproductive system ciliated epithelium in thefallopian tubes move the egg from the uterus to the ovary. Motile cilia also known as flagella, drive the sperm cells.[88]Invertebrateplanarians have ciliated excretoryflame cells.[89] Other excretory cells also found in planarians aresolenocytes that are long and flagellated.
Plastids divide by binary fission.Vacuoles in plant cells store water, and are surrounded by a membrane.[92] The vacuoles of plant cells are usually larger than those of animal cells. The vacuole membrane transports ions against concentration gradients.[93]
The plant cytoskeleton is a dynamic structure that has a scaffold of microtubules and microfilaments, but not the intermediate filaments.[94] Themicrotubule organizing center in plant cells is often sited underneath the cell membrane where nucleated microtubules often form sheet-like semi-parallel arrays.[95]
There are two types of peroxisomes in plants. One type is in the leaves where it takes part inphotorespiration. The other type is in germinating seeds where they take part in the conversion of fatty acids into sugars for the plant's growth.[74] In this peroxisome type the enzymatic content is so different than in other groups that it has an alternative name ofglyoxysome, their enzymes are of theglyoxylate cycle.[75]
The cells offungi have in addition to the shared eukaryotic organelles aspitzenkörper in their endomembrane system, associated withhyphal tip growth. It is aphase-dark body that is composed of an aggregation of membrane-bound vesicles containing cell wall components, serving as a point of assemblage and release of such components intermediate between the Golgi and the cell membrane. The spitzenkörper is motile and generates new hyphal tip growth as it moves forward.[98]
Human cancer cells, specificallyHeLa cells, with DNA stained blue. The central and rightmost cell are ininterphase, so their DNA is diffuse and the entire nuclei are labelled. The cell on the left is going throughmitosis and its chromosomes have condensed.
In meiosis, the DNA is replicated only once, while the cell divides twice. DNA replication only occurs beforemeiosis I. DNA replication does not occur when the cells divide the second time, inmeiosis II.[104] Replication, like all cellular activities, requires specialized proteins.[23]
Cell signaling is the process by which a cell interacts with itself, other cells, and the environment. Typically, the signaling process involves three components: the first messenger (the ligand), thereceptor, and the signal itself.[105] Most cell signaling is chemical in nature, and can occur with neighboring cells or more distant targets. Signal receptors are complex proteins or tightly bound multimer of proteins,located in the plasma membrane orwithin the interior.[106]
Each cell is programmed to respond to specific extracellular signal molecules, and this process is the basis ofdevelopment,tissue repair,immunity, andhomeostasis. Individual cells are able to manage receptor sensitivity including turning them off, and receptors can become less sensitive when they are occupied for long durations.[106] Errors in signaling interactions may cause diseases such ascancer,autoimmunity, anddiabetes.[107]
Proteins can be targeted to the inner space of anorganelle, different intracellularmembranes, theplasma membrane, or to the exterior of the cell viasecretion.[108][109] Information contained in the protein itself directs this delivery process.[109][110] Correct sorting is crucial for the cell; errors or dysfunction in sorting have been linked to multiple diseases.[109][111][112]
Between successive cell divisions, cells grow through the functioning of cellular metabolism. Cell metabolism is the process by which individual cells process nutrient molecules. Metabolism has two distinct divisions:catabolism, in which the cell breaks down complex molecules to produce energy andreducing power, andanabolism, in which the cell uses energy and reducing power to construct complex molecules and perform other biological functions.[114]
Complex sugars can be broken down into simpler sugar molecules calledmonosaccharides such asglucose. Once inside the cell, glucose is broken down to make adenosine triphosphate (ATP),[23] a molecule that possesses readily available energy, through two different pathways. In plant cells,chloroplasts create sugars byphotosynthesis, using the energy of light to join molecules of water andcarbon dioxide.[115]
Cells are capable of synthesizing new proteins, which are essential for the modulation and maintenance of cellular activities. This process involves the formation of new protein molecules fromamino acid building blocks based on information encoded in DNA/RNA. Protein synthesis generally consists of two major steps:transcription andtranslation.[63]
Transcription is the process where genetic information in DNA is used to produce a complementary RNA strand. This RNA strand is then processed to givemessenger RNA (mRNA), which is free to migrate into the cytoplasm. mRNA molecules bind to protein-RNA complexes calledribosomes located in thecytosol, where they are translated into polypeptide sequences. The ribosome mediates the formation of a polypeptide sequence based on the mRNA sequence. The mRNA sequence directly relates to the polypeptide sequence by binding totransfer RNA (tRNA) adapter molecules in binding pockets within the ribosome.[63] The new polypeptide then folds into a functional three-dimensional protein molecule.
Unicellular organisms can move in order to find food or escape predators. Common mechanisms of motion includeflagella andcilia.[36]
In multicellular organisms, cells can move during processes such as wound healing, the immune response andcancer metastasis. For example, in wound healing in animals, white blood cells move to the wound site to kill the microorganisms that cause infection. Cell motility involves many receptors, crosslinking, bundling, binding, adhesion, motor and other proteins.[116] The process is divided into three steps: protrusion of the leading edge of the cell, adhesion of the leading edge and de-adhesion at the cell body and rear, and cytoskeletal contraction to pull the cell forward. Each step is driven by physical forces generated by unique segments of the cytoskeleton.[117][116]
In August 2020, scientists described one way cells—in particular cells of a slime mold and mouse pancreatic cancer-derived cells—are able tonavigate efficiently through a body and identify the best routes through complex mazes: generating gradients after breaking down diffusedchemoattractants which enable them to sense upcoming maze junctions before reaching them, including around corners.[118][119][120]
A separate mode of cellular death is known as amitotic catastrophe, which occurs duringmitosis, following the improper progression of, or entrance to thecell cycle. This mechanism operates to prevent genomic instability.[123][124]
Stromatolites are left behind bycyanobacteria, known as blue-green algae. They are among the oldest fossils of life on Earth. This one-billion-year-old fossil is fromGlacier National Park in the United States.
Cells emerged around 4 billion years ago.[127][128] The first cells were most likelyheterotrophs. The early cell membranes were probably simpler and more permeable than later ones, with only a single fatty acid chain per lipid. Lipids spontaneously form bilayeredvesicles in water, and could have preceded RNA.[129][130]
The first evidence of multicellularity in an organism comes fromcyanobacteria-like organisms that lived between 3 and 3.5 billion years ago.[139] Cyanobacteria are variable in morphology,filamentous forms exhibit functional cell differentiation such asheterocysts (for nitrogen fixation),akinetes (resting stage cells), andhormogonia (reproductive, motile filaments). These, together with the intercellular connections they possess, are considered the first signs of multicellularity.[140]
Multicellularity was made possible by the development of theextracellular matrix (ECM) similar in function to the bacterial ECM that consists of extracellular polymeric substances.[141] EPS enables microbial cell adhesion, and is believed to be the first evolutionary step toward multicellular organisms.[142]Basement membranes are a type of specialized extracellular matrix that surrounds mostanimal tissues, and are essential in their formation. Their emergence coincided with the origin of multicellularity.[143]
In 1665,Robert Hooke examined a thin slice of cork under hismicroscope, and saw a structure of small enclosures. He wrote "I could exceeding plainly perceive it to be all perforated and porous, much like ahoneycomb, but that the pores of it were not regular".[144] To further support his theory,Matthias Schleiden andTheodor Schwann studied cells of both animal and plants. What they discovered were significant differences between the two types of cells. This put forth the idea that cells were fundamental to both plants and animals.[145]
^Cooper, Geoffrey M. (2000)."The Origin and Evolution of Cells".The Cell: A Molecular Approach. 2nd edition. Sinauer Associates. Retrieved17 September 2025.
^Egan, Elizabeth S.; Fogel, Michael A.; Waldor, Matthew K. (2005). "MicroReview: Divided genomes: negotiating the cell cycle in prokaryotes with multiple chromosomes".Molecular Microbiology.56 (5):1129–1138.doi:10.1111/j.1365-2958.2005.04622.x.PMID15882408.
^Saier Jr., Milton H.; Bogdanov, Mikhail V. (2013). "Membranous Organelles in Bacteria".Microbial Physiology.23 (1–2):5–12.doi:10.1159/000346496.PMID23615191.
^Kim, K. W. (2017). "Electron microscopic observations of prokaryotic surface appendages".Journal of Microbiology.55 (12):919–926.doi:10.1007/s12275-017-7369-4.PMID29214488.
^abcBeeby, Morgan; et al. (May 2020). "Propulsive nanomachines: the convergent evolution of archaella, flagella and cilia".FEMS Microbiology Reviews.44 (3):253–304.doi:10.1093/femsre/fuaa006.PMID32149348.
^abKhan, Yusuf S.; Farhana, Aisha (2025)."Histology, Cell".StatPearls. StatPearls Publishing. Retrieved15 October 2025.
^"Inside the Cell"(PDF).publications.nigms.nih.gov. Archived fromthe original(PDF) on 28 July 2017. Retrieved22 September 2025.
^Singer, S. J.; Nicolson, Garth L. (February 18, 1972). "The Fluid Mosaic Model of the Structure of Cell Membranes: Cell membranes are viewed as two-dimensional solutions of oriented globular proteins and lipids".Science.175 (4023):720–731.doi:10.1126/science.175.4023.720.PMID4333397.
^abcAlberts, Bruce (2015).Molecular biology of the cell (6th ed.). New York: Garland science, Taylor and Francis group. pp. 666–667.ISBN978081534464-3.
^Mauro A (April 1969). "The role of the Voltaic pile in the Galvani-Volta controversy concerning animal vs. metallic electricity".J Hist Med Allied Sci.24 (2):140–50.doi:10.1093/jhmas/xxiv.2.140.PMID4895861.
^Haycraft, Courtney J.; Serra, Rosa (2008-01-01), "Chapter 11 Cilia Involvement in Patterning and Maintenance of the Skeleton",Current Topics in Developmental Biology, Ciliary Function in Mammalian Development,85, Academic Press:303–332,doi:10.1016/s0070-2153(08)00811-9,ISBN978-0-12-374453-1,PMC3107512,PMID19147010
^Björn, Lars Olof; Govindjee (2009). "The evolution of photosynthesis and chloroplasts".Current Science.96 (11 June 10, 2009):1466–1474.JSTOR24104775.
^Sato, N. (2006). "Origin and Evolution of Plastids: Genomic View on the Unification and Diversity of Plastids". In Wise, R. R.; Hoober, J. K. (eds.).The Structure and Function of Plastids. Advances in Photosynthesis and Respiration. Vol. 23. Springer. pp. 75–102.doi:10.1007/978-1-4020-4061-0_4.ISBN978-1-4020-4060-3.
^abNelson DL (January 2017).Lehninger principles of biochemistry. Cox, Michael M.,, Lehninger, Albert L. (Seventh ed.). New York, NY.ISBN978-1-4641-2611-6.OCLC986827885.{{cite book}}: CS1 maint: location missing publisher (link)
^abcdLodish, Berk, Kaiser, Krieger, Bretscher, Ploegh, Martin, Yaffe, Amon (2021).Molecular Cell Biology (9th ed.). New York, NY: W.H. Freeman and Company.ISBN978-1-319-20852-3.{{cite book}}: CS1 maint: multiple names: authors list (link)
^D'Arcy, Mark S. (June 2019). "Cell death: a review of the major forms of apoptosis, necrosis and autophagy".Cell Biology International.43 (6):582–592.doi:10.1002/cbin.11137.PMID30958602.
^Vitale I, Galluzzi L, Castedo M, Kroemer G (June 2011). "Mitotic catastrophe: a mechanism for avoiding genomic instability".Nat Rev Mol Cell Biol.12 (6):385–92.doi:10.1038/nrm3115.PMID21527953.
^Orgel, L. E. (December 1998). "The origin of life--a review of facts and speculations".Trends in Biochemical Sciences.23 (12):491–495.doi:10.1016/S0968-0004(98)01300-0.PMID9868373.
^abcdLatorre, A.; Durban, A; Moya, A.; Pereto, J. (2011)."The role of symbiosis in eukaryotic evolution". In Gargaud, Muriel; López-Garcìa, Purificacion; Martin, H. (eds.).Origins and Evolution of Life: An astrobiological perspective. Cambridge: Cambridge University Press. pp. 326–339.ISBN978-0-521-76131-4.Archived from the original on 24 March 2019. Retrieved27 August 2017.
^Niklas, Karl J.; Newman, Stuart A. (January 2013). "The origins of multicellular organisms".Evolution & Development.15 (1):41–52.doi:10.1111/ede.12013.PMID23331916.
^abGest, H. (2004). "The discovery of microorganisms by Robert Hooke and Antoni Van Leeuwenhoek, fellows of the Royal Society".Notes and Records of the Royal Society of London.58 (2):187–201.doi:10.1098/rsnr.2004.0055.PMID15209075.S2CID8297229.
^Hooke, Robert (1665).Micrographia: ... London: Royal Society of London. p. 113.... I could exceedingly plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular [...] these pores, or cells, [...] were indeed the first microscopical pores I ever saw, and perhaps, that were ever seen, for I had not met with any Writer or Person, that had made any mention of them before this ... – Hooke describing his observations on a thin slice of cork. See also:Robert HookeArchived 1997-06-06 at theWayback Machine
