The work of Charles Rennie Mackintosh was a critical bridge between Art Nouveau and early Modernism. The lecture explains how Mackintosh moved away from excessive ornamentation toward clarity, simplicity, and functional planning, while still retaining symbolic and craft-based elements. Focusing on the Glasgow School of Art, the session highlights ideas such as mechanomorphic architecture, asymmetry within symmetry, rational plans based on function, and innovative use of light, section, and material contrast. The lecture also traces how Mackintosh’s emphasis on structure, light-filled interiors, and restrained façades influenced later modernist thinking and set the stage for 20th-century architectural developments.