Our daily internal clocks are controlled by genes, which are small units of DNA passed down from our parents. These genes contain the code to produce proteins—molecules in the body that carry out specific jobs. Some of the genes that control our internal clocks produce proteins called "activators" and others produce proteins called "suppressors." Activators are proteins that turn a gene on, whereas suppressors are proteins that turn a gene off. In our daily internal clocks, we need two activators to bind together to turn on a gene. This gene is usually turned on in the morning. Once this gene is turned on, lots of different proteins are made, including the two suppressors. When there are lots of these suppressor proteins being made, we typically feel energetic and lively! Throughout the day, the concentration of these suppressor proteins increases in our bodies. By the evening, enough suppressor proteins are made to block the activators and turn off the gene. While you sleep, the suppressors in the bloodstream break down. During this breakdown, which occurs at nighttime, we feel tired and sleepy.

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