What is Cell?
{{otheruses}} [[File:DAPIMitoTrackerRedAlexaFluor488BPAE.jpg|300px|right|thumb|[[Endothelium|Endothelial]] cell: [[nuclei]] stained blue, [[mitochondria]] stained red, and [[F-actin]], a component of microfilaments, stained green. Cell imaged on a fluorescent [[microscope]].]] In [[biology]], the '''cell''' is the basic structure of [[organism]]s. All cells are made by the [[cell division|division]] of other cells. The [[environment]] outside the cell is separated from the [[cytoplasm]] inside the cell by the [[cell membrane]]. Inside some cells, parts of the cell stay separate from other parts. These separate parts are called [[organelle]]s (like small [[Organ (anatomy)|organs]]). They each do different things in the cell. Examples are the [[Cell nucleus|nucleus]] (where [[DNA]] is), and [[mitochondria]] (where [[chemical energy]] is converted).<ref>Alberts B. ''et al.'' 2002. ''Molecular biology of the cell''. 4th ed, Garland.</ref><ref>Lodish H. ''et al.'' 2004. ''Molecular cell biology''. 5th ed, WH Freeman: NY.</ref> [[File:celltypes.svg|thumb|450px|The cells of [[eukaryote]]s (left) and [[prokaryote]]s (right)]] == Kinds of cells == Cell can be divided into different types depending on the structure of the nucleus and the physiological function. In 1957 cells were divided into two types based on the structure of nucleus. These were the [[Prokaryote|prokaryotic]] cell and the eukaryotic cell. Prokaryotes, such as [[bacteria]] and [[archaea]], are simple cells that have no [[cell nucleus]]. They do have [[bacterial microcompartment]]s. Eukaryotes are complex cells with many organelles and other structures in the cell. They are larger than prokaryote cells: they can be as much as 1000 times greater in volume. Eukaryotes store their [[genetic]] information ([[DNA]]) on [[chromosome]]s in the [[cell nucleus]]. [[Organism]]s (living things) which are made up of multiple cells are eukaryotes. Most cells are small, the largest just being seen by the human eye (egg cell). They need to be small in order to