Modern architecture is characterized by a modern aesthetic focusing on plain geometric forms and the principle of 'form follows function.' Key materials include steel and reinforced concrete, allowing new construction methods like skyscrapers, with influential schools such as the Chicago School, Werkbund, and Bauhaus shaping its evolution. Prominent architects like Louis Sullivan, Walter Gropius, and Ludwig Mies van der Rohe played significant roles in its development, contributing innovative designs and concepts that have left a lasting impact on the field.