Young star clusters are key to understanding star formation in galaxies, with the interplay of star formation, feedback, and gas cycling within them and the surrounding ISM having direct implications for their host galaxies. Observations with JWST in lensed fields have revealed that young star clusters in galaxies in the early Universe have systematically distinct conditions: they are more compact, dense and metal-poor compared to those in weakly star-forming galaxies in the local Universe, and dominate the rest-frame UV/optical emission of their host galaxies. 

In this talk, I will present insights obtained from theoretical models, and state-of-the-art radiation-hydrodynamic simulations of star cluster formation and evolution in this regime, and highlight several key outcomes of star cluster formation unique to this extreme regime. I will demonstrate that these outcomes have observational implications on their host galaxies, and may be central to understanding several outstanding issues raised by JWST in the early Universe.