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[[دوتنه:Epithelial-cells.jpg|بټنوک|يوه سټېن شوې ژونکه]]
'''ژونکه''' د ژوند يو بنسټيز فعال واحد دی. د لومړي ځل لپاره [[روبېرټ هوک]] دا وموندل چې ژونکه د ټولو ژونديو اورګانيزمونو يو عملي واحد دی، او ټول ژوندي له همدغه واحد نه جوړ دي. په ژوندي اورګانيزمونو کې دا تر ټولو وړوکی واحد دی، چې د ژوند د رامنځ ته کېدو د خښتې په توګه هم ياده شوې.<ref name="Alberts2002">[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&term=Cell+Movements+and+the+Shaping+of+the+Vertebrate+Body+AND+mboc4%5Bbook%5D+AND+374635%5Buid%5D&rid=mboc4.section.3919 Cell Movements and the Shaping of the Vertebrate Body] in Chapter 21 of ''[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&term=cell+biology+AND+mboc4%5Bbook%5D+AND+373693%5Buid%5D&rid=mboc4 د ژونکې ماليکيولي ژونپوهنه]'' څلورم چاپ, سمونګر Bruce Alberts (2002) published by Garland Science.<br /> The Alberts text discusses how the "cellular building blocks" move to shape developing [[embryo]]s. It is also common to describe small molecules such as [[amino acid]]s as "[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&term=%22all+cells%22+AND+mboc4%5Bbook%5D+AND+372023%5Buid%5D&rid=mboc4.section.4#23 molecular building blocks]".</ref> Some organisms, such as most [[bacteria]], are [[unicellular]] (consist of a single cell). Other organisms, such as [[human]]s, are [[multicellular]]. Humans have about 100 trillion or 10<sup>14</sup> cells; a typical cell size is 10 [[micrometre|µm]] and a typical cell mass is 1 [[nanogram]]. The largest cells are about 135 µm in the [[Anterior horn of spinal cord|anterior horn in the spinal cord]] while [[granule cells]] in the [[cerebellum]], the smallest, can be some 4 µm and the longest cell can reach from the toe to the lower [[brain stem]] ([[Pseudounipolar neuron|Pseudounipolar cells]]).<ref>{{YouTube|id=EvrWHa1PLUQ|title=Integrative Biology 131 - Lecture 03: Skeletal System}} first 12 minutes of the lecture covers cells (by Marian Diamond).</ref> The largest known cells are unfertilised [[ostrich]] [[Ovum|egg cells]] which weigh 3.3 pounds.<ref>{{cite book | last = Campbell | first = Neil A. | authorlink = | coauthors = Brad Williamson; Robin J. Heyden | title = Biology: Exploring Life | publisher = Pearson Prentice Hall | date = 2006 | location = Boston, Massachusetts | pages = | url = http://www.phschool.com/el_marketing.html | doi = | id = | isbn = 0-13-250882-6 }}</ref><ref>{{cite web|author=Mitzi Perdue |url=http://www.eggscape.com/birds.htm |title=Facts about Birds and Eggs |accessdate=2010-04-15}}</ref>
In 1835, before the final cell theory was developed, [[Jan Evangelista Purkyně]] observed small "granules" while looking at the plant tissue through a microscope. The [[cell theory]], first developed in 1839 by [[Matthias Jakob Schleiden]] and [[Theodor Schwann]], states that all organisms are composed of one or more cells, that all cells come from preexisting cells, that vital functions of an organism occur within cells, and that all cells contain the [[genetics|hereditary information]] necessary for regulating cell functions and for transmitting information to the next generation of cells.<ref>{{cite book
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| first = Anthea
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| coauthors = Hopkins, Jean Johnson, Susan LaHart, David Quon Warner, Maryanna Wright, Jill D
| title = Cells Building Blocks of Life
| publisher = Prentice Hall
| year = 1997
| location = New Jersey
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| isbn = 0-13-423476-6}}</ref>
The word ''cell'' comes from the [[Latin]] ''cellula'', meaning, a small room. The descriptive term for the smallest living biological structure was coined by [[Robert Hooke]] in a book he published in 1665 when he compared the [[Cork (material)|cork]] cells he saw through his microscope to the small rooms monks lived in.<ref name="Hooke">"<cite>... 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. . .</cite>" – Hooke describing his observations on a thin slice of cork. [http://www.ucmp.berkeley.edu/history/hooke.html Robert Hooke]</ref>
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