It's impossible to imagine Japanese meals without soy sauce, or the umami-rich fermented bean paste called miso, or the rice-based spirit known as sake. Which means that Japanese cuisine depends on the one fungus that enables the fermentation of all these delicious foods: koji. Today, American chefs are discovering what Asian cooks have known for centuries, that koji is a microbial powerhouse with seemingly magical abilities to completely transform food. But how does a mold from a family of microbes known for their toxicity turn salty, mashed beans into sticky, succulent miso? How did koji make its way from Japan to the U.S.? And how might the weird and wonderful ways chefs in the U.S. are now using koji transform the American dinner table, too?