The Mikrokosmos is a cycle of 153 pieces written for piano, graded according to difficulties. Bartók produced the compositions for his son Peter, for his piano lessons.
As Peter himself wrote, " So were born some of the easier pieces in these volumes. However, he kept on producing others at a much faster rate than I could learn them."
Bartók explained that the first four volumes of Mikrokosmos were written to provide study material for the beginner pianist. Work on Volume 4 may - indeed should - be combined with the study of other compositions ...