In astronomy, numerical simulations bound our theory to observations. But what do these simulations represent, and how do we create them? For this ScientiFika, I will talk about cutting edge research done here at Stockholm University in the “Cosmology and AI group”, where we attempt to infer the starting point of our Universe in order to simulate a “digital twin” of the observed large-scale-structure and the galaxies that fill it. I will discuss how these kind of simulations go beyond the current state-of-the-art in pushing our understanding of how our Universe formed, and where we need to look to learn more