The dancers are dressed in early-style leotards. The leotard became more popular as practice wear in the 1960s. Jules Leotard, a 19th-century French acrobat, invented the leotard. Leotards were mostly used by circus performers and gymnasts until the 1960s. Dancers were then expected to have something similar to what you see today under their costumes. Before the leotard, dancers wore short dresses or tights with loose-fitting pants. These were often made of fabric that was easy to move in (such as silk) but not very protective (because they were not meant to cover up). They could also be skin-tight (like a ballet tutu). Dancing is thought to have originated in Greece around 1500 B.C. But it wasn't until much later that people started wearing clothes for entertainment purposes. The ancient Greeks would dress up in colorful costumes and dance at festivals. This was probably where the tradition of wearing clothes for fun came from. It may have been natural for people to want to follow this tradition when doing other types of exercise such as running or jumping. In the 15th century, Italian dancers began wearing tight-fitting garments called pantaloons. This must have been how the leotard got its name. Later on in the 16th century, French dancers started wearing leotards too.