| Abstract: | Strong gravitational lensing (SL) is nowadays at the very heart of important issues in modern cosmology, which I will address in my talk. SL allows, 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. Firstly, I will discuss the impact of systematic errors in the SL modeling of galaxy clusters by analyzing two state-of-the-art simulated clusters, with the same characteristics as those from the Hubble Frontier Fields clusters but particularly on the recovery of robust cosmological. I will also discuss the potential of SL clusters to uncover high-redshift galaxies that allows us to probe the reionization epoch. We take advantage of the recent RELICS survey to analyze a set of SL clusters, map their DM distribution and characterize the properties of background z~6 galaxies. |