According to scientific research, a healthy posture needs to be dynamic, based on frequently changing the sitting position. Changing the posture consciously not only prevents backache, it also avoids unilateral strain. The D1 chair series placed the implementation of this basic principle at the very heart of its design. The aim was to promote a seating behaviour in which form, function and ergonomics work together in an almost symbiotic manner. This was achieved thanks to a sophisticated concept that incorporates the user and his or her behaviour. The seat and backrest of this chair adapt flexibly to changing postures, possessing a functionality that actively encourages users to sit in a dynamic fashion. The key part of the design is an innovative mechanism that is integrated into a visible joint below the seat. Distinctively innovative about it is that this mechanism allows the seat and backrest to tilt independently around four axes. The tubular steel frame is linked to and anchored within the joint. Thus, the seat and the backrest become flexible and, depending on the posture, tilt independently forwards and backwards, while also pivoting to both sides. This principle introduces a larger motion radius and has been implemented into the classic office chair as well as into the conference and lounge chairs of the collection.