In the current issue of Nature Photonics, Prof. Dr. Oliver G. Schmidt, Dr. Libo Ma and partners present a strategy for observing and manipulating the optical Berry phase in Möbius ring microcavities. In their research paper, they discuss how an optical Berry phase can be generated and measured in dielectric Möbius rings. Furthermore, they present the first experimental proof of the existence of a variable Berry phase for linearly or elliptically polarized resonant light.