Once upon a time there was a poor Camel. He was going through the dry desert and he couldn't find any water around. He has been going for a couple of months. The Camel was very sad and thirsty, he even didn't have any tears to cry. But ,suddenly, the poor Camel saw something bright on the horizon! It was a little puddle. He was very happy! The Camel drank so much water at once! And after he decided to keep some water inside his body, just in case there is no more water around for the next couple of months. So there is a hump on the Camel's back.