An early bird rises with the sun, springing out of bed abuzz with energy. Meanwhile, a night owl groggily rises much later, not hitting their stride until late in the day. How many people are truly night owls or early birds? And are our sleep schedules predetermined at birth, or can we change them? Explore how our circadian systems act as internal clocks to keep our bodies functioning properly. This TED-Ed lesson was directed by Avi Ofer, narrated by Alexandra Panzer and the music is by André Aires.