Hector Guimard (1867 – 1942) was a French architect and designer, and a prominent figure of the Art Nouveau style. He achieved early fame with his design for the Castel Beranger, the first Art Nouveau apartment building in Paris, which was selected in an 1899 competition as one of the best new building facades in the city. He is best known for the glass and iron canopies, with ornamental Art Nouveau curves, which he designed to cover the entrances of the first stations of the Paris Metro.
Castel Beranger
The Castel Béranger is a residential building with thirty-six apartments located at 14 rue de la Fontaine in the 16th arrondissement of Paris. It built between 1895 and 1898. It was the first residence in Paris built in the style known as Art Nouveau.
The Paris Metro
Between 1900 and 1913, Hector Guimard was responsible for the first generation of entrances to the underground stations of the Paris Métro. His Art Nouveau designs in cast iron and glass dating mostly to 1900, and the associated lettering that he also designed, created what became known as the Métro style and popularized Art Nouveau.
Hector Guimard had a long career designing buildings. His Art Nouveau period was short, limited to the turn of the century. The style went out of fashion and after World War I, the world had run out of the money required for exuberant buildings.
Books and web sites detailing Hector Guimard are widely available. Wikipedia offers a very good summary of his work and provides many links elsewhere.