Shrinking shirt?

I just put a shirt in the washing machine... and it shrunk from a women's medium to... well, close to a child's medium. I put the cycle on cold and delicate. The material was rayon... I am just wondering if anyone knows why this happened... an answer...

would be greatly appreciated so that I don't repeat my mistake a second time. Thank you!

rayon does that, especially if its 100% next time buy a rayon/cotton, or rayon/polyester mix, good luck

It just does that. Rayon is the type you usually have to take to the dry cleaners.