From breakfast toast to evening wine, yeast is the microscopic thing that we cannot live without. We knew what yeast did as an invisible brewer and baker long before we had a clue about the existence of microorganisms. Ten thousand years ago, our ancestors abandoned bush meat and wild fruit in favor of farming animals and cultivating grain. Leaving the forests and grasslands, our desire for beer and wine produced by the fungus was a major stimulus for agriculturalsettlement. It takes a village to run a brewery or tend a vineyard. We domesticated wild yeast and yeast domesticated us. With the inevitable escape of the fungus from beer vats into bread dough, our marriage with yeast was secured by an appetite for fresh loaves of leavened bread. Over the millennia, we have adapted the technologies of brewing, winemaking, and baking and have come to rely on yeast more and more. Yeast produces corn ethanol and other biofuels and has become the genetically-modified darling of the pharmaceutical business as a source of human insulin and a range of life-saving medicines. These practical uses of yeast have been made possible by advances in our understanding of its biology, and the power of genetic engineering has been used to modify thefungus to do just about anything we wish. We know more about yeast than any other organism built from complex cells like our own. To understand yeast is to understand life. In this book Nicholas P. Money offers a celebration of our favorite microorganism.