Today, biomineralisation s.l. processes constitute a growing branch of research within the fast evolving field of geomicrobiology. These processes include those influenced and/or induced by microorganisms referring as organomineralization (Dupraz et al. 2009). The study of these processes was already among the multiple scientific interests of F.-A. Forel ! As early as the second half of the 19th century he confirmed some of the findings of other contemporaneous Swiss naturalists. In the third volume of his renowned book “Le Léman” he mentioned …les naturalistes neuchâtelois ont étudié les sculptures admirablement développées sur les galets de la rive des lacs du pied du Jura, et les ont attribuées à l'action d'une algue Cyanophyscée… From this starting point he further speculated about the nature of the bio-chemical processes involved in the precipitation of these lacustrine carbonates. At the time many of the advanced hypothesis remained as such due to the lack of detailed knowledge about these organisms, their metabolisms and the associated chemical reactions that they may produce. This was due to methodological limitations that did not allow the observation and monitoring of these microorganisms neither in situ nor in the laboratory. How far have we gone since Forel's early observations ? In this contribution we summarize the results of very recent investigations carried out in the shallow area of western Lake Geneva (Switzerland) that demonstrate, as forecasted by Forel and other contemporaneous naturalists, the critical role of cyanobacteria in the formation of ooids or carbonate coated sand grains.