ONCE UPON A TIME, you were so small that you weren’t even visible to the human eye. You were just a cell in your mother’s womb, a single microscopic speck. And then you became two cells . . . then four cells . . . then eight cells, and those cells kept multiplying, copying and differentiating until you became a hundred trillion cells, each with a distinct purpose: brain cells and skin cells and heart cells and stomach cells and blood cells, cells that produce tears and cells that produce milk and cells that make you sweat and cells that grow hair and cells that help you see.
The hand that is holding this