The first inhabitants of planet Earth were single-celled microorganisms and they are still with us today. Their name is truly legion, for they live everywhere, from boiling hot springs at the Earth's surface and on the seafloor to the coldest waters of the oceans and the Antarctic lakes. They are the masters of evolutionary adaptation, who have colonized the entire range of conditions under which water can exist as a liquid. At some ancient mythic time billions of years ago in a witches' brew of precursory molecules, somewhere, somehow, on a sunny Precambrian day bright with promise some of these molecules came together in the first coupling, learned to replicate, create enzymes, metabolize, and seal themselves into protective membranes inside of which they began the process of living. How they did this is our greatest mystery, for they are our primordial ancestors and we do not understand ourselves until we understand them.