The elephant is a creature of epic proportions- and yet, it owes its enormity to more than 1,000 trillion microscopic cells. And on the epically small end of things, there are likely millions of unicellular species, yet there are very few we can see with the naked eye. Why is that? Why don't we get unicellular elephants? Or blue whales? Or brown bears? Murry Gans explains. [4:06]