1. In the 500s BC, a poet named Thespis is credited with innovating a new style in which a solo actor performed the speeches of the characters in the narrative.
2. In 471 BC, the dramatist Aeschylus innovated a second actor, thus making dialogue between characters possible onstage.
3. Around 468 BC, Sophocles introduced a third actor making more complex dramatic situations possible. Three actors subsequently became the formal convention.
1. In the 500s BC, a poet named Thespis is credited with innovating a new style in which a solo actor performed the speeches of the characters in the narrative.
2. In 471 BC, the dramatist Aeschylus innovated a second actor, thus making dialogue between characters possible onstage.
3. Around 468 BC, Sophocles introduced a third actor making more complex dramatic situations possible. Three actors subsequently became the formal convention.
from http://www.crystalinks.com/greektheater.html