Sunflowers Circadian Rhythm

Scientists have known for centuries that sunflowers track the Sun across the sky,
turning their flowers from east to west as the day progresses. But a team of
scientists has finally been able to figure out exactly how this happens.
It turns out that sunflower swings are caused by an internal circadian rhythm, or
body clock, and this daily shift in position not only improves the flowers' leaf
size, but also makes them more attractive to bees.