Functionalism is an architectural style that emphasizes form following function. It originated with Louis Sullivan and was popularized by Le Corbusier. Key features include low ornamentation, an emphasis on materials, and a focus on a building's purpose. Examples discussed include Le Corbusier's Unite d'Habitation and the Lotus Temple in Delhi. Brutalism developed from functionalism and is characterized by sculptural concrete forms and an emphasis on texture and raw materials. Pioneering Brutalist architects mentioned include Le Corbusier, Louis Kahn, and Paul Rudolf.