Observations of the local and high-z Universe confirm that star formation is an inherently clumpy and clustered process and, as a consequence, the physical properties of star clusters are expected to be intimately linked with those of their hosts. In particular, the long-lived massive star clusters can be used to trace galaxy assembly and the gas properties at the time of their formation, and they may be one of the primary sources of reionization of the Universe. 

This field is currently undergoing a revolutionizing phase. Large surveys carried out with ground and space based telescopes (such as Gaia, HST, Euclid, ALMA, ESO/VLT) have enabled unprecedented photometric and spectroscopic studies in the Local Universe and the JWST’s access to rest-frame optical wavelengths at z>3 along with the magnification power of gravitational lensing are opening a new era in the study of the star-forming modes well within the reionization epoch allowing us to directly probe star cluster formation and constrain unprecedented/unexpectedly dense stellar systems as possible sites of GC formation. 

The formation and evolution of star clusters is inherently a multi-physics and multi-scale problem, involving star formation and feedback, galaxy formation and evolution, N-body dynamics, stellar and binary evolution. As a consequence, the broad range of interconnected issues concerning the study of star clusters and their host galaxies can be addressed only with an interdisciplinary approach. 

In this exciting and rapidly changing context, we aim at bringing together observers and theorists from both the local and high-z Universe communities. The goal is to inspire discussions and exchange ideas about how to perform a transformative leap in the field, build a comprehensive picture of star cluster formation and evolution, explore the link between old massive, young star clusters and high-z proto-globular clusters, their connection to galaxy formation and their potential role in the reionization of the Universe. Focus will be given to how efficiently leverage available observations spanning different spatial, temporal and physical scales, along with those that will be soon on-line thanks to the several upcoming new giant facilities (such as E-ELT, Vera Rubin Telescope, Nancy Grace Roman Space Telescope, GMT), and the new generations of dynamical and cosmological hydro-dynamical simulations at spatial scales suitable to resolve stellar clusters.