what do capillaries do?
<answer> They are tiny blood vessels which allow only very few blood cells to get through at a time. <context> This is not perceptible to the human eye. Capillaries are tiny blood vessels which allow only very few blood cells to get through at a time. When blood cells enter the capillaries, the oxygen and nutrients which are stored in hemoglobin in the blood diffuse into the body. The exhausted blood cells then enter back into larger vessels to join the bloodstream once again. The cycle goes something like this: