Biology
Molecular mechanisms of circadian rhythms in nocturnal rodents
Quick fact
In nocturnal rodents, the core clock genes CLOCK and BMAL1 activate transcription of Per and Cry genes, whose own proteins then inhibit CLOCK and BMAL1, forming a feedback loop that takes about 24 hours to complete.
Why this is interesting
Picture a mouse that runs on its wheel at the same time every night, even in constant darkness. How does its body know when it's time?