What better way to start than with the cell itself. My first thought would be to make it some sort of power cell.
What I would also need to do is design it in such a way that it can believably divide into two of the same cells without the cell just morphing. Have you ever seen solid metal simply morph into two duplicates as if it were made of mercury?
I think a cylindrical object would be the best option due to the simplicity of how it would divide; simple screw-bottom and top.