ELI5: How do sunflowers follow the sun?

Imagine you're a little kid and you really love playing outside. You especially love the sun because it's warm and makes you feel good. So, you try to face the sun all day, turning your head as it moves across the sky.

Sunflowers do something similar! They're like little solar panels wanting to soak up as much sunlight as possible.

Here's how they do it:

• Young sunflowers have a special trick. They have a part in their stem that grows faster on the east side in the morning. This pushes the flower head towards the rising sun in the east.

• During the day, the west side of the stem grows faster than the east. This slowly turns the flower head to follow the sun as it moves across the sky towards the west.

• This isn't magic! It's caused by special plant hormones called auxins. These hormones are like tiny messengers that tell the stem to grow. More auxins on one side of the stem makes it grow faster.

• At night, the sunflower slowly turns back to face east to get ready for the sunrise. Scientists aren't 100% sure how they do this, but they think it might be like a "reset" using their internal clock.

• Old sunflowers, once they're fully grown and have heavy seeds, usually stop tracking the sun and face east. This is because they don't need as much sunlight anymore, and facing east might help them warm up faster in the morning.