Bartók's Mikrokosmos has been one of the milestones in pedagogical piano repertoire for 80 years - and yet it is also far more than a "classical" piano primer. These 153 piano pieces, organized in ascending order of difficulty, engage not only with technical aspects of piano playing but also with the fundamentals of composition - from "Imitation and Inversion," "Ostinato," and "Free Variations," concerning compositional technique, to mood pieces and pieces with programmatic ideas such as "Notturno," "Boating," "From the Diary of a Fly," or the famous "Six Dances in Bulgarian Rhythm." Mikrokosmos first appeared in 1940 in six volumes. Based on volume 40 of the Bartók Complete Edition published in 2020 (Z. 15040), the present Urtext edition offers the series gathered in three volumes. This edition includes Bartók's preface, exercises, and notes written for the first edition. Furthermore, it also features a preface and comments by the editor, which not only discuss the genesis and the compositional sources but also provide performers, teachers and pupils alike, with authentic and detailed information about Bartók's notation and the specific performing problems of Mikrokosmos.