Computer-driven machines that mix, knead, rise, punch down, bake and sometimes cool bread. The ingredients are measured and added to a single, nonstick canister, which becomes mixing bowl, baking pan and oven. A motor-driven blade in the canister's base mixes and kneads the dough; a heating coil handles the baking. Bread machines come in many models, but there are three basic loaf shapes: vertical rectangle, horizontal rectangle and cylindrical. There are several capacities available, ranging from 1/2-pound to 2-pound loaves. It's important to follow manufacturer's directions (which can vary) for adding and layering ingredients. Failing to do so could prevent the yeast from mixing with the liquid, which would result in a failed loaf of bread.