A tutu is a special kind of skirt the dancers wear. The first tutus were floor length gowns with heavy decorations worn in the royal courts in the 15th and 16th centuries. But these were very big and heavy, making it hard for the dancers to move.
In the early 1800s, with the introduction of the pointe shoe and the creation of many fairy tales about nymphs and other worldly creatures, the Romantic tutu became popular. This tutu comes just below the dancers’ knees and is dreamy and ethereal but also allows them to move more freely.
As ballet technique developed, becoming more complicated and challenging, the tutu was shortened to just above the knee. This bell-shaped tutu is known as a Classical tutu. It was much easier for dancers to perform in and the audience could see the positions of the legs and the dazzling footwork.
Choreographers and costume designers in the 21st century now choose costumes which best suit the purpose of their ballets. This means that depending on the ballet, you may see a Romantic tutu, a Classical tutu or no tutus at all!