That's my Grandma!
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How can that be? Well, when both a wet and a dry place are connected by a tube of water, the water always flows towards the dry area (like a sponge). Our roots are surrounded by water underground. Our leaves, high up in the tree, lose water through the pores on their surface. That's why our leaves are always drier than our roots. And since water always flows to the dry area, it always moves from our wet roots toward our drier leaves.
A second force also helps us: the fact that water molecules stick to each other. So, as a water molecule evaporates from the surfaces of a leaf, the molecule right behind it is pulled up by that attraction. And so on, all the way down the line, to the bottom of our roots.
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