The Second Person in God, the Son, became human Himself: was born into the world as an actual man—a real man of a particular height, with hair of a particular color, speaking a particular language, weighing so many stone. The Eternal Being, who knows everything and who created the whole universe, became not only a man but (before that) a baby, and before that a fetus inside a woman’s body. If you want to get the hang of it, think how you would like to become a slug or a crab.
C.S. Lewis, Mere Christianity