The sea urchin egg, 100 microns, is approximately the same size as a human egg. Up through gastrulation, development is also similar. BUT, it is a lot easier to extract millions of eggs from sea urchins than from mammals of any kind. By proper husbandry, we can keep sea urchins gravid year round and use them to study the early events of development.

Topics have included:

Calcium, NO and IP3
Protein and DNA synthesis
Peroxide production
pH changes
Lipid metabolism
Oxygen use
Metamorphosis
Apoptosis

See then our web site devoted to teaching students about early development:

Sea Urchin Embrology: http://www.stanford.edu/group/Urchin