Espresso
Anatomy of an espresso machine
Boiler · pump · grouphead · steam wand
Water from a tank or plumb-in is heated in a boiler, pushed by a pump to ~9 bar, and forced through a grouphead — a saturated brass block that keeps temperature steady. The portafilter locks into the grouphead, holding a basket of coffee. A separate (or shared) boiler makes steam for milk. PID controllers hold temperature within ±0.5°C — invisible from the outside, decisive in the cup.