Cells were recognized by Robert Hooke in 1665. One of the main differences between unicellular organisms and multicellular organisms is that unicellular organisms have one cell and are small, and multicellular organisms have more than one cell in them and are large. Unicellular organisms fall under the classification of prokaryotes because their structure isn’t complicated. Considering there is no nucleus in prokaryotes, this leads to their impotence to handle their surface area to volume ratios. Thus, the area a unicellular organism takes up is small-it’s the opposite for multicellular organisms. Multicellular organisms like algae can have a nucleus; which lets them manage their surface area to volume ratio. As the cell gets larger, the surface area to volume ratio gets smaller. Therefore, if the cell grows exceeding a definite perimeter, not enough material will be capable of traversing the membrane swiftly enough to harbor the enlarged cellular volume. When this occurs, the cell must allocate into smaller cells with the favorable surface area to volume ratios, or terminate function. The requirements for life in a cell are having a way of storing information (Deoxyribonucleic acid), a way of producing fuel (adenosine triphosphate synthase), a means of duplicating for reproduction, and a cell membrane. Since a unicellular organism only has one cell, the cell must be able to carry out all these functions. A multicellular organism is large because there needs to be more than one cell in order for the functions to be carried out. The definition of growth is becoming greater in size and multicellular organisms grow by producing cells (this is one of the requirements for life in a cell: reproduction). Every inner bit of the cell has to be provided by part of the cell exterior. While a cell develops larger, its inside mass enlarges and the cell membrane enlarges. Sadly, the amount of volume expands more quickly than does the exterior area, and so the total of surface area obtainable to progress materials to a component volume of the cell smoothly reduces. Eventually, there’s enough surface accessible to service the interior; if it is to thrive, the cell must cease its growth.