One of the works, probably less known, of Antoine van Leeuwenhoek (1632-1723) is his Arcana naturae detecta (Detected secrets of nature) published in its first edition in 1695. This work is a compilation of 38 letters on scientific issues and it is beautifully illustrated. A nota-ble section of the work is the observation and description for the first time of fermentation yeasts and his experiments on the spontaneous generation of microorganisms.