Memory foam pillows are made out of specially treated polyurethane that is designed to retain its initial shape after a night of use. As you can guess, the major advantage of memory foam pillows is that they're extremely supportive, which makes them a good option for people with back or neck problems. Memory foam pillows are an especially good choice for side sleepers, who "like how the pillow does not cause their nose to sink into it as is often the case with fibrous and down pillows." One aspect of memory foam pillows that may take some getting used to is their sensitivity to temperature, which is what gives them their "contouring" properties: They're firmer when cold and less firm when warm. Memory foam pillows are more resistant to dust mites than other varieties.