Alvar Aalto

Stool 60, launched in 1933, may be the most useful object on this list: three birch legs bent into an L at the top using a technique Aalto developed with the cabinetmaker Otto Korhonen, screwed directly under a round seat, so the stools stack in a neat spiral and serve as seats, side tables or plant stands. It is cheap, light and nearly indestructible. The Paimio chair, a bent-plywood seat designed for tuberculosis patients to breathe easily, shows his comfort research. He and his wife Aino Aalto co-founded Artek in 1935 to sell the furniture.