An article published in the journal “Nature” reports the results of a study on the formation of a primordial galaxy cluster, observed in its early stages. A team of researchers led by Luca Di Mascolo of the University of Trieste, Italy, used the ALMA radio telescope to study the intracluster medium, the gas that permeates the protocluster around the galaxy MRC 1138-262, known as the Spiderweb Galaxy, and has an overall mass greater than the mass of the galaxies that form it. Observations of the intracluster medium in forming clusters are scarce, making those observations precious to understand the formation processes of galaxy clusters.