Capillary Action
Capillary action is the way water travels upward through narrow spaces on its own, like when a paper towel soaks up a spill.
Think of it this way
Stand a paper towel upright in a shallow dish of colored water. The water climbs up the towel on its own, without anyone pushing it. Tiny gaps between the towel fibers pull the water upward, like a chain of hands passing a bucket from one to the next. The narrower the gaps, the higher the water climbs.
Explaining capillary action by grade level
When you dip a paper towel into water with dissolved candy colors, watch what happens. The water climbs up the paper all by itself. It moves through tiny gaps in the paper, pulling the colors along with it. The water holds onto the paper and pulls itself higher, one tiny step at a time.