Complex sentence: Born in Chicago, Illinois, he began acting in live theatre while still in his teens then embarked on a film career in 1912 with the Chicago-based Selig Polyscope Company then joined Essanay Studios in 1914.
Split into simpler sentences: Born in Chicago, Illinois, he began acting in live theatre while still in his teens. Lester then embarked on a film career in 1912 with the Chicago-based Selig Polyscope Company then joined Essanay Studios in 1914.