I still remember the first time I cupped two Ethiopians side by side—same harvest, same region, same roaster—one a classic washed lot, the other a natural, fruit-splashed experiment. The natural tasted like strawberry jam had been sun-kissed on the rim of the cup. The washed felt like jasmine and lemon peel drifting through clean spring water. Same coffee plant, wildly different cups. The invisible artists behind those differences? Yeasts and microbes work quietly during fermentation.