The current thinking is that, as cells become larger, the volume increases faster than the surface area. Doubling the volume will double the number of metabolic reactions, but since the surface area...
A unit of an organism that can only be seen with the help of a microscope.
Well there is one that is not microscopic. It's macroscopic which means it can be seen by the naked eye, the egg's yolk.
I believe it's because they are so tiny you need a microscope to see them. :)
anything you look under a microscope