The Second City, based out of Chicago, Illinois, is a training center that specializes in improvisational comedy. Improvisational theatre, often called improv or impro, is the form of theatre, often comedy, in which most or all of what is performed is unplanned or unscripted: created spontaneously by the performers. In its purest form, the dialogue, action, story, and characters are created collaboratively by the players as the improvisation unfolds in present time, without the use of an already prepared, written script.