Baby's little nose is in full working order at birth. He knows your scent well from the time he spent in the womb, and studies show that newborns can tell the difference between their mother's breast pads and those of another nursing mom by scent. Babies are born preferring sweet smells like the fragrance of vanilla; lemon is also a favorite. And your newborn naturally dislikes foul odors, like the smell of rotten eggs. He also hates bitter or sour tastes — probably an instinct to help him avoid dangerous foods.