Why must the cells of multicellular organisms differentiate

Multicellular organisms are more complex and it the organism such as a human did not differentiate the cells would not be able to compensate for all the functions that the body has developed through evolution

I think because they need to have variation plus it is not just a must but because multi-cellular organisms are sexual reproduction not asexual reproduction it allows for variation.

The proton has a positive charge while the neutron has no charge they both make up the nucleus of the atom while the elections have a negative charge and surround the nucleus of the atom. the protons and electrons are used to calculate the atom's mass whereas the neutrons don't affect the mass

  a. chromosomes are duplicated before cell division so that each new daughter cell has a complete set