"Rolled oats" is the everyday name for the flattened flakes of Avena sativa, but in the kitchen it stands for a whole family of processed oat forms that behave very differently in the pot. All begin as the same hulled groat and diverge only in how that groat is cut, steamed and pressed: whole groats stay intact and chewy, steel-cut (pinhead, Irish) oats are the groat chopped into gravel, stone-ground oatmeal is the groat milled to meal for porridge, old-fashioned rolled oats are groats steamed and squashed into broad flakes, and quick and instant oats are pressed thinner (and, for instant, pre-cooked) so they cook in minutes. The choice is a texture and time decision — steel-cut for nubbly, risotto-like porridge over half an hour; rolled for creamy stovetop oatmeal, granola, flapjacks and cookies; instant for a 60-second bowl — much as long-grain, short-grain and parboiled are culinarily distinct forms of one rice.