You have most likely heard of black holes, very fascinating and at the same time mysterious celestial bodies of the universe with such a high gravity that it does not let even light escape. However, not everyone knows that General Relativity also admits the existence of celestial bodies that have exactly the opposite behavior to that of black holes: white holes. From these hypothetical regions of space-time nothing can enter from the outside, but at the same time matter, light or energy can exit. Simply put, it would be the exact opposite of a black hole. The existence of white holes is only theoretical and there is no certain proof of their existence, but some theories state that black holes and white holes can be connected. In this sense, everything that is "captured" by a black hole would be ejected from a white hole, connected to it, in any other part of the universe. Another peculiarity of white holes would concern time: In the vicinity of these areas, time could even flow in reverse! Since they have never been observed and there is no evidence of their existence, white holes remain at the moment only a theoretical question. However, being predicted by General Relativity, and knowing that, until now, General Relativity perfectly reflects reality, we can be confident that in the not so distant future these celestial bodies may actually be discovered somehow.