O thou invisible spirit of wine, if thou hast no name to be known by, let us call thee devil!
— Cassio, William Shakespeare’s Othello
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We humans have enjoyed alcoholic beverages for millennia, but our grasp of yeast’s role in fermentation goes back a mere 150 years. In that century and a half, though, scientists, brewers, and bakers have made enormous strides. While our understanding of fermentation remains incomplete, we know enough to reliably and repeatedly coax favorable results from yeast (Saccharomyces, at least).