Sea Urchin And Human

Sperm Comparison

Note The 5 Micron Size.

Remember 1000 microns = 1 mm, 25 mm = 1 inch

Egg Comparison

Note The 100 Micron Size.

This image is about 20 times less magnified than the sperm illustration above. 100 microns is about the limit of resolution of the human eye. If you look closely at sea urchin eggs in a beaker, you can distinguish individual eggs.