The story of Medusa started with her as a human maiden who is only boastful for her own beauty, and believed to be the most beautiful woman of Athens, Greece.
Once she visited the Acropolis, where there lived a sculpture of the wisdom goddess Athena, Medusa had fallen into deep jealousy due to everybody enjoying the beauty of Athena instead of her.
The beautiful, sassy Medusa just wanted to be inspired by the Athenians more than Athena. She made selfish comments about the artwork in the temple. Everyone gasped when they overheard her. They became horrified that Athena would do something really bad to Medusa.
Athena did hear her! She appeared into Medusa's reflection on the bronze doors of the temple. Furious, the goddess confronted Medusa for her threats.
For her punishment, the goddess changed Medusa into a monster, called a Gorgon, with scale skin, snakes for hair, and the ability to turn people into stone by looking into her hideous eyes.
At the end of Medusa's story, one demigod named Perseus entered the home of the Gorgon sisters and beheaded Medusa by using a mirror-like shield (without looking directly at her) and his sword.