Modern dance is a style of performance that emerged in the late 19th and early 20th centuries as a reaction against the strict rules of classical ballet. It emphasizes creativity, expression, and individuality, allowing dancers to explore a wide range of movements and emotions. Unlike ballet, which often follows a set structure, modern dance encourages improvisation and personal interpretation. Key figures in the development of modern dance include Martha Graham, Isadora Duncan, and Merce Cunningham. These pioneers introduced new techniques and philosophies, focusing on the body's natural movements and the use of space. Today, modern dance continues to evolve, incorporating elements from various styles and cultures.