Every espresso shot is a 25-second chemistry experiment. Water at 93 degrees and 9 bars of pressure dissolves over 1,000 compounds from ground coffee in a precise sequence — bright acids first, then sugars and caramels, and finally bitter tannins. Understanding this sequence lets baristas dial in flavor by adjusting grind, dose, and time to land in the sweet spot between sour under-extraction and bitter over-extraction.