Dining out on diatoms

the colourful interference of diatom shells (bottom panel). More than a hundred years on, and with the use of modern illumination and photography, Möller's original preparations reveal why they may have fascinated many a dinner party. Imagine a dinner party where the host, instead of serving dessert, invites you to take a look down the microscope in the drawing room. And instead of a digestive you gaze at minuscule algae. Hard to believe today, when the best or worst you can expect is a holiday video, but in posh salons of the 9 th century this was not an uncommon occurrence. A current exhibition (Zoologisches und Botanisches Museum) now documents extraordinary examples of such enlightened entertainment. The exhibition features microscopic preparations by the German optical entrepreneur Johann Diedrich Möller (844– 907). Möller applied his dexterity to arranging microorganisms into highly decorative patterns using horsehairs as tools. In particular, he dedicated himself to diatoms — single-celled algae that are encased in two half-shells of polymerised silicate. Diatoms defy the conventional wisdom that we find beautiful only what is sufficiently rare. Their shells exhibit a stunning diversity of delicate ornaments, and yet diatoms are among the most abundant living things on Earth. They are particularly abundant in the oceans — close to half of the ocean's primary production and about one fifth of plant-generated oxygen are diatom-derived. Given their abundance, diatom shells quickly became an object of fancy among microscopists, as soon as microscope power sufficed to resolve their intricate shell patterns. Möller tapped into this emerging market by dealing in microscopic preparations of diatom shells that served as guides for identification or intended to reflect diatom diversity in a given habitat (top panel). But Möller also draped kaleidoscopic patterns for aesthetic purposes, exploiting Draped diatoms: Möller's original preparations showing diatoms from one specific habitat (top) and a 'salon preparation' (bottom).