Modern theatre's origins in the late 19th and early 20th centuries marked a shift towards realism and social critique. Playwrights like Ibsen and Chekhov explored complex characters and societal issues, while movements like Naturalism and Symbolism emerged. This era saw innovations in stagecraft, acting techniques, and thematic content. Stanislavski's system revolutionized acting, while playwrights tackled taboo subjects and challenged societal norms. These changes laid the foundation for contemporary theatre practices and themes.