Actually, nothing actually shrinks. Just drawn up closer to the body for warmth.

I was told to take cold showers to shrink then I thought about it and said no to drugs just like the time the riddler tried to kill batman while riding on the carribean boat that was smaller than minnie mouses ears which offended me more than any story of mother goose which slightly freaked out the little kid in different strokes who said that he experimented with drugs but that's a whole nother story.