We used a lidar to measure polar mesospheric clouds from a balloon floating in the upper stratosphere. The thin-layered ice clouds at 83 km altitude are perturbed by waves. The high-resolution lidar soundings reveal small-scale structures induced by the breaking of those waves. We study these patterns and find that they occur very often. We show their morphology and discuss associated dynamical physical processes, which help to interpret case studies and to guide modelling.