Because Tempur's Pressure Relieving Material is temperature sensitive and visco-elastic, the pillow will actually respond to your body temperature and mass to mould to the natural curvature of your head and neck, thereby aligning them perfectly with your spine. The open cells shift under pressure and reposition themselves to gently cradle your head and neck to help alleviate pain and provide a more restful night's sleep. The open cells allow air to circulate throughout the pillow, keeping you cooler and more comfortable than a regular pillow.