During recent decades, strong gravitational lensing has become a powerful tool to study astronomical objects with widely different physical scales. It has also proven to be a promising diagnostic that can solve outstanding problems in cosmology. Now is a critical time for strong lensing research, as forthcoming large surveys (Euclid, Roman Space Telescope, Rubin Observatory and CSST) will map the entire sky and increase the number of known lenses from a few hundred to around 100, 000. Concurrently, observations of lenses with current and forthcoming instruments (ALMA, JWST, E-ELT) will spatially resolve scales that are beyond the reach of telescopes for objects in the distant Universe. These new data will revolutionise our understanding of galaxy and structure formation, and offer unprecedented cosmological applications. In IAU Symposium 381, members of observational and theoretical communities review our preparedness for this new era, to discuss advanced statistical techniques, and to foster new collaborations.
