Why can colored water be seen flowing up through a celery stalk?

Celery is a plant that has very thin and hollow tubes that run through its stems. When you place a celery stalk in colored water, the water is drawn up through these tiny tubes by a process called capillary action. This is because the water molecules are attracted to the walls of the tubes, which causes them to move upwards. The colored water can then be seen flowing up through the stalk.