The laminar similarity solution of the boundary layer on a rotating disk in still ambient fluid was presented by von Kármán more than 100 years ago. A cross-flow instability was discovered in 1955 through flow visualisation experiments, and that instability has since then been investigated through stability analysis, experiments and numerical simulations. Other studies have investigated if an absolute instability could explain the distinct transition Reynolds number seen in experiments. Later experiments and stability theory have taken on both broad and slender cones to elucidate the influence of the cone apex angle on stability and transition. If you are interested to contribute with research on rotating bodies the present paper can be seen as a guideline—quo vadis.