Also called a crockpot, the slow cooker is an electric "casserole" that cooks food with low, steady, moist heat. It's designed to cook food over a period of 8 to 12 hours. These appliances range in size from 1 to 6 quarts. Slow cookers can cook a dish while you're at work, and they don't heat up the kitchen. On the minus side is that some vegetables (like celery) can become mushy before the other ingredients are done.