Photo: 'OMG' Microscope Lives Up to Its Name

[adieu]

8. If this question isn't a joke

fission is what an atom does, resulting in multiple product atoms of different atomic numbers, and some random freed up neutrons and possible beta particles (electrons), plus some energy.

Mitosis breaks a cell into two identical cells. Each cell contains millions of atoms. In order to split into two identical cells, there has to be enough material (atoms, strung together as molecules, in particular amino acids) to do so. Or, it has to be split into two baby cells and grow into mature cells.