The whole body has 30 trillion cells in it. You would think that you're just trying to get blood equally to these 30 trillion cells. But the kidney, which is only 100 grams in size, not very big at all, is getting 20% of the whole blood. The kidneys have this disproportionate requirement. Extremely. And that's because not because the tissue necessarily needs to be fed a lot, but because the role that the kidneys play is filtering that blood and needs to constantly filter the blood.