According to one version of the Greek story, Medusa was once a lovely young girl who had a boyfriend she loved very much. One afternoon she and her boyfriend were looking for a place where they could be alone, and they went into a temple of the goddess Athena. Seeing that nobody else was there, they sat down to talk, and soon they started to kiss.
Athena, looking down from the sky, saw Medusa kissing her boyfriend, and Athena was very angry that they would use her temple this way. Athena made Medusa grow very ugly, and have snakes instead of hair.
Medusa's boyfriend ran away, frightened.
After that Medusa went away from other people and hid herself, and she lived with her sisters (who had also gotten ugly) for many years. They were so ugly that if you looked at them you would turn into a stone statue!
To find out more about Medusa, check out these books on Amazon or at your local library:
Snake Hair: The Story of Medusa (All Aboard Books Reading Level 2)
by Stephanie Spinner and Susan Swan. A beginning reader book, just a few sentences on each page, and big pictures done with paper collage. My daughter and I loved this one.
Say Cheese, Medusa! Myth-O-Mania, by Kate McMullan (2002). A "cool" retelling of the story, with a lot of puns, for kids.
D'aulaire's Book of Greek Myths, by Edgar and Ingri D'Aulaire.
Medusa: Solving the Mystery of the Gorgon, by Stephen R. Wilk (1999). For adults. Traces the story of Medusa using the ancient sources (writing and art) and then through the centuries to modern times.