"Silk is preferred for bedtime for the slippery transitions when changing positions in sleep," says Imm. "Silk naturally moves with your body, whereas cotton and other materials don't move as effortlessly against the materials of your sheets and blankets." Silk is also a top choice for pajamas due to its ability to thermoregulate. Linen is lightweight but durable enough to last a long time. And of course, cotton breathes well, making it too a top choice. Polyester is less breathable and not recommended if you lean warm when sleeping.