We wanted a totally new kind of chair. So we turned to the two designers who had produced the groundbreaking Equa chair and asked them to start with a clean slate and no assumptions. A bold challenge!

So Don Chadwick and Bill Stumpf began their work of thinking about what a chair ought to do for a person by consulting people who spend a lot of time in their chairs-older people in retirement centers. Chadwick and Stumpf came to some solid conclusions.

Ergonomically, a chair ought to do more than just sit there. It should actively intercede for your health when you sit in it longer than you should.

Functionally, it ought to move and adjust as simply and naturally as possible. It should support you in any position you assume, at any task your office job serves up.

Anthropometrically, a chair ought to be inclusive. It should do more than accommodate people who are larger or smaller than average size-it should really fit them.

Environmentally, it ought to be benign. Its manufacture should be sparing of natural resources, and the chair itself should be durable and easy to repair, recyclable and easy to disassemble.

The design that met these criteria redefined the very meaning of "work chair." It wasn't upholstered. It wasn't padded. It was dimensioned in three models that looked exactly alike and that had nothing to do with their people's job titles. It didn't look like any other office chair. And its revolutionary concept incorporated more patentable ideas than any previous Herman Miller research program.

It was a matter of deliberate design to create a 'new signature shape' for the Aeron chair, says designer Bill Stumpf. "Competitive ergonomic chairs became look-alikes. Differentiation was a huge part of the Aeron design strategy, and it remains one of, if not the most, critical aspects of Aeron's success.

"The human form has no straight lines; it is biomorphic. We designed the chair to be, above all, biomorphic, or curvilinear, as a metaphor of human form in the visual as well as the tactile sense. There is not one straight line to be found on an Aeron chair."

And what about the lack of cushions? Says Bill Stumpf, "The Pellicle was equally a deliberate design strategy in that its transparency symbolizes the free flow of air to the skin in the same way lace, window screens, and other permeable membranes permit the flow of air or light or moisture. The transparency of the chair as a visual element was in keeping with the idea of transparent architecture and technology, which Aeron pioneered in advance of Apple's transparent iMac computers. Transparency is a major design movement. Its purpose is to make technology less opaque, to communicate the inner workings of things, and to make objects less intrusive in the environment. Aeron is a nonintrusive chair."

The Aeron design was refined and validated through research and experts' opinions: It was tested for comfort with scores of users, pitting it against the best work chairs available. Leading ergonomists, orthopedic specialists, and physical therapists evaluated the chair's fit and motion, the benefit and ease of its adjustments. The design team conducted anthropometric studies across the country, using a specially developed instrument to calculate everything from popliteal (back of the knee) height to forearm length.

The research team did pressure mapping and thermal testing to determine the weight distribution and heat- and moisture-dissipating qualities of the Pellicle material on the chair's seat and back. Field studies using a specially designed measuring device examined the relationship between sizes of people and their preference for chair size (Dowell 1995b). Measurements of 224 people-in a sample that was evenly distributed between men and women and that closely reflected the distribution of the U.S. population on most dimensions-found that of all the anthropometric dimensions measured, height and weight had the strongest relationship to chair size preference. The relationship is strong enough to allow us to recommend one of the three chair sizes based on those dimensions.

Although it reveals its aesthetic heritage in lyrical shapes reminiscent of George Nelson designs, organic forms that recall the work of Charles Eames, and a spare, athletic aspect that brings to mind its designers' Equa chair, the Aeron chair finally looks only like itself. Its unique form expresses its purpose and use and the material composition of its parts and the way they connect. The slightly transparent and reflective nature of its surfaces gives it an airy quality. It becomes a part of the person who uses it and the environment that surrounds it.

Made largely of recycled materials, the Aeron chair is designed to last a long time, and parts that get the most wear are easily replaced and recycled. Just what you would expect in a well thought-out design.