Have you ever stopped to think about what goes on inside a tree? We know that the roots of a tree take up water and minerals from the soil and transport them to the leaves where some of the water is used in photosynthesis to combine with carbon dioxide from the air to make sugars, starches and cellulose. But the roots are 20-30 feet below the top of the average Hill Country tree, and there are many trees that are several times that tall.