An American in Paris and the origins of the stereomicroscope.

A century ago, Horatio S. Greenough, an American living in Paris, persuaded the firm of Carl Zeiss to construct the first low-power stereomicroscope. Fitted by Zeiss with Porro prisms for image erection, this instrument became the ancestor of all stereoscopic dissection microscopes ("binoculars") now in use. On the basis of original documents and earlier publications, the present Centennial Essay traces both the history of the Greenough stereomicroscope and the scantily documented life of its inventor, including his probable descent from a family of famous New England sculptors. The aim is to provide some historical background for a truly timeless instrument that was fundamental to developmental biology, beginning almost from the days of its proclamation by Wilhelm Roux.