  It is widely accepted that stars do not form in isolation but result from the
fragmentation of molecular clouds, which in turn leads to star cluster
formation. Over time, clusters dissolve or are destroyed by interactions with
molecular clouds or tidal stripping, and their members become part of the
general field population. Star clusters are thus among the basic building
blocks of galaxies. In turn, star cluster populations, from young associations
and open clusters to old globulars, are powerful tracers of the formation,
assembly, and evolutionary history of their parent galaxies. Although their
importance had been recognised for decades, major progress in this area has
only become possible in recent years, both for Galactic and extragalactic
cluster populations. Star clusters are the observational foundation for stellar
astrophysics and evolution, provide essential tracers of galactic structure,
and are unique stellar dynamical environments. Star formation, stellar
structure, stellar evolution, and stellar nucleosynthesis continue to benefit
and improve tremendously from the study of these systems. Additionally,
fundamental quantities such as the initial mass function can be successfully
derived from modelling either the H-R diagrams or the integrated velocity
structures of, respectively, resolved and unresolved clusters and cluster
populations. Star cluster studies thus span the fields of Galactic and
extragalactic astrophysics, while heavily affecting our detailed understanding
of the process of star formation in dense environments.This report highlights
science results of the last decade in the major fields covered by IAU
Commission 37: Star clusters and associations.
