Ypsilon Chair Vitra 1998 Atelier Bellini		In 1994 Herman Millers Aeron chair radically transformed the office seating market. In response Vitra's tasked Mario Bellini to develop a competing product that would be as comfortable and iconic. I had just joined the Bellini office in 1996 and I then spent months in the workshop manually optimising springs and harmonic steel to achieve a backrest that would change dynamically to support the widest possible range of postures. However all attempts to apply a spring-based backrest for mass production were not economically viable until I finally devised and prototyped a simplified structure that would use the elastic properties of plastic. Mario Bellini, loved it and transformed the idea into the iconic Y-shape. For the first time in office seating was the comfort designed for three dimensional freedom of movement. There is no frame in the backrest to obstruct body movement and all parts have been balanced between support, flexibility and user adjustability. After its introduction in 1998, the design and comfort principles of the Ypsilon chair have proven even more influential than those of the Aeron chair. Ironically Vitra has discontinued any chair using the Y-shape, whereas the comfort principles has been adopted by Herman Miller and currently being refined in new generation of task chairs.