If you're feeling a bit on the short side, measure yourself when you first wake up. This phenomenon may be due to gravity compressing cartilage in our spine and in other parts of our bodies, such as our knees when we stand up or sit down throughout the day. "While we are lying down in a resting position, the spine is said to "spread out" or decompress, so when we wake in the morning we are taller after lying in bed all night."