In 1940 Walt Disney got the idea for the first ever nature documentary True Life Adventures during animal studies for his upcoming film Bambi. Instead of imitating the natural through animation, he could just use what was already there. When the sun rises and light enters through the eyelids the body is triggered to begin its wake-up cycle, including the release of cortisol. By the time the light is at full brightness, sleepers wake up on their own. An alarm is not needed anymore.