For the first time scientists, led by ICREA Prof. Raul Jimenez, have developed a method to look into our past Universe. The so-called “past-light-cone” are those regions of the Universe that remain unconected from us because it would take light longer than the age of the Universe to travel. In principle we cannot explore this vast region of our Universe. However, by using galaxy clusters as “cosmic mirrors” Jimenez et al. have shown that one could actually view these regions of our past. The technique involves making “movies” of the cosmic microwave background: the relic of the most distant light in the early Universe. This new observational window could open new avenues to understand nature as we do not know if the Universe in its past is like ours or different. It would allow us to peer into causaly disconnected regions from us and thus understand if the pillars of physical cosmology (which received the nobel prize this year) are correct or we will discover new physics.