Recently, some of the most massive and disturbed clusters have been the centre of attention thanks to the Hubble Frontier Fields (HFF) initiative, which constitutes the largest commitment ever of HST time to the exploration of the distant Universe via gravitational lensing by massive galaxy clusters. These clusters were chosen for their strong lens properties, and are all highly disturbed objects, showing major and minor merging on-going processes, making them ideal target to trace the Cosmic Web assembly.

While combining strong and weak-lensing regimes to map the total mass with X-rays observations of the hot gas and spectroscopy of cluster galaxies to look at their direction of motion, we can thus study the dynamical scenarios in place within these massive galaxy clusters, and trace the sub-structures engaged in these processes.

I will present a new multi-wavelength picture of the three most massive HFF clusters. The depth of these dataset makes these clusters amazing Cosmic Telescopes, but also enables us to get an unprecedented understanding of the cluster physics. I will present a comparison of the dark matter, light and gas distributions, that will lead us to the distribution of substructures within the MACSJ0416, MACSJ0717 and Abell 2744 vicinities. Finally I will discuss the different clues that these observables provide on the evolution processes in massive galaxy clusters.