Data collected during LHC Run 2 open the window to increasingly rare processes of top quark production. Furthermore, new analysis techniques lead to large improvements in sensitivity. We report the first observation of the production of a single top quark with a Z boson (tZq) in final states with three leptons, based on data collected by the CMS experiment in the years 2016 and 2017 at a centre-of-mass energy of 13 TeV. The measured cross section is compatible with standard model predictions. The presentation will also include further recent CMS results on top physics.