Choosing a pillow for side sleeping can be surprisingly difficult. A pillow may feel comfortable when you first lie down, yet feel too flat, too firm, or awkward after you have been sleeping on it for a while. The difference often comes down to how its height, shape, and support work with your head, neck, shoulder, and mattress. Instead of asking only, “What is the best pillow for side sleepers?” start with a more useful question: What does your body need from a pillow while