When studying various issues of tectonics in the mines of the Prokopyevsk‑Kiselevsk region, I paid special attention to the study of folds developed within one layer or even in part of a layer. Hence, these folds are called microfolds or intralayer folds. The development of microfolding is observed not only in the mines of Kuzbass, Donbass or other coal basins, but also in all folded areas. However, different researchers attached different significance to this phenomenon, and the origin of microfolds was often interpreted incorrectly, without connection with observations of the actual material.