Celery stalk
1 tablespoon (15 milliliters) of red food colouring
Tall, clear jar
Enough water to fill half the jar

Here's how

Pour the water in the jar. Add the red colouring.

Stand the celery in the glass.

Wait 24 hours, and the celery leaves will turn red.

Why?

The celery absorbs the water—and the colouring—and carries it to the leaves. Plants absorb water and minerals in a process called osmosis. In osmosis liquids pass through a plant's membrane, or outer covering, and move through its stem to its leaves.