Our modern lifestyle – characterized by low light exposure during the day and high light exposure during the evening and nighttime hours – has dramatic effects on circadian rhythms and, ultimately, our ability to fall asleep and stay asleep. The key to restoring those rhythms to their natural, healthy patterns may be as simple as making small changes that alter the amount and timing of our exposure to light. In particular, exposure to 30 to 40 minutes of bright light, early in the day, and exposure to lower light during the afternoon and evening hours can reset our internal clocks and improve our sleep. In this clip, Dr. Matthew Walker explains how altering the timing and duration of daytime light exposure influences sleep.