> What I've always wondered is about cells. They split and multiply and grow, and if it all starts from this one little microscopic cell, where do all the atoms and molecules for what eventually becomes a full-grown human come from? They're obviously not packed into that one little cell.
>
> -Eric Sleator

This is why you consume food and liquids -- you're providing building material for the cells of your body (among other important things, such as energy for the living ones).

Stephen