Greek drama exemplifies the earliest form of drama of which we have substantial knowledge. Tragedy, as a dramatic genre, developed as a performance associated with religious and civic festivals, typically enacting or developing upon well-known historical or mythological themes. Tragedies generally presented very serious themes. With the advent of newer technologies, scripts written for non-stage media have been added to this form. War of the Worlds (radio) in 1938 saw the advent of literature written for radio broadcast, and many works of Drama have been adapted for film or television. Conversely, television, film, and radio literature have been adapted to printed or electronic media.