Ballet involves the creation of the dance itself, often a type of imaginary story. The story is told with the help of dance and mime. Ballet is a form of expression. It presents a story in a new form to the audience. The creation of a dance is called choreography. The choreography is learnt by the dancers under the supervision of a trainer, called a ballet master or mistress. Ballet is always performed to music, and in many cases the music was specially composed for a particular ballet. Ballet is a major part of theatre, and a popular example is "The Nutcracker".