Coffee is the roasted seed — the "bean" — of the coffee cherry (Coffea arabica and C. canephora), ground and steeped in hot water to make the world's most widely drunk caffeinated beverage. Roasting turns a hard, grassy green seed deeply bitter and brown, layering it with hundreds of roasty, caramel, nutty and chocolatey aromas, while its caffeine makes it a mild stimulant.