Strong gravitational lensing (SL) is nowadays at the very heart of important issues in modern cosmology, allowing for instance to map the dark matter (DM) distribution of galaxy cluster’s cores, to image very high redshift sources otherwise too faint to be detected or to constrain the geometry of the Universe, which I will address in my talk.
Taking advantage of the recent RELICS project to analyze several SL clusters, we have mapped their DM distribution and characterize the properties of background z~6 galaxies that can probe the reionization epoch with future follow-up.
Finally, I will present the potential of SL clusters to put constraints on cosmological parameters related to dark matter and dark energy.