The advent and development of large-scale time domain surveys are revealing the existence of a large and diverse zoo of transients; common transients that can be used as tools to constrain GR or cosmological parameters, and rare & exotic transients that are observed for the first time. The origin of the transients is often unknown, but linked to stellar systems and interactions. In this talk I will show novel channels to induce stellar interactions and subsequent transients -in electromagnetic radiation as well as gravitational waves, ranging from stellar mergers to gravitational wave sources. Amongst others I will discuss the potential of triple stars as GW progenitors: while triple star systems are common (even more common than binaries for massive stars!), our understanding of their evolution has lagged behind compared to single and binary stars. Dr. Toonen will be hosted by Fabian Schneider (fabian.schneider@h-its.org)