At first, ballets were woven in to the midst of an opera to allow the audience a moment of relief from the dramatic intensity. By the mid-seventeenth century, Italian ballets in their entirety were performed in between the acts of an opera. Over time, Italian ballets became part of theatrical life: ballet companies in Italy's major opera houses employed an average of four to twelve dancers; in 1815 many companies employed anywhere from eighty to one hundred dancers.