Stellar cluster research is in a dynamic state. IAU Symposium 351 (also chosen as MODEST-19, within the 'Modelling and Observing DEnse STellar systems' meeting series) is a compilation of the research presented at the Symposium. It contains highlights of the latest research taking place in many areas, including the formation of stellar clusters at high redshifts, multiple stellar populations within stellar clusters, the dynamical evolution of stellar clusters, and the production of exotic objects such as black holes within stellar clusters. This volume also includes articles on the build up of larger galaxies from smaller galaxies and stellar clusters, and discussions of the latest data from large surveys and from the Gaia satellite. Looking at both the local and the high-redshift universe allows links to be established between the clusters we see today and their progenitors. IAU S351 is an ideal entry point for astronomers new to this research field.

Dense stellar systems lie at the interface between dynamics, stellar evolution, and galaxy formation, and they provide us with an ideal laboratory to understand many different aspects of these important fields as well as to explore the interplay between them. The complete study of dense stellar systems is a very challenging task which requires the collaboration and the exchange of ideas of astronomers and physicists with observational and theoretical expertise in galactic and extra-galactic astronomy, stellar dynamics, hydrodynamics, stellar evolution, as well as knowledge of many aspects of computational physics. IAU Symposium 246 brought together experts in all these areas to cover the broad field of dense stellar systems with particular emphasis on the interplay between them and on the comparison between observations and simulations. This volume provides a complete review of the most recent studies in this topical research.