Patty and Mildred Hill are the most famous composers you've never heard of.

They came up with "Happy Birthday to You!" in an effort to make something all children could easily sing. They ended up with a tune the whole world loved.

"Happy Birthday to You!" has been sung to presidents and kings, on big stages and in outer space. And it all started in a kindergarten classroom with a teacher coaxing her children to sing an easy tune all together.