This image is an artist's impression of the water snow line around the young star V883 Orionis, as detected with the Atacama Large Millimeter/submillimeter Array (ALMA). ALMA has made the first ever resolved observation of a water snow line within a protoplanetary disc. This line marks where the temperature in the disc surrounding a young star drops sufficiently low for snow to form. A dramatic increase in the brightness of the young star V883 Orionis flash heated the inner portion of the disc, pushing the water snow line out to a far greater distance than is normal for a protostar, making it possible to observe it for the first time. The idea of snow orbiting in space is fundamental to planet formation. The presence of water ice regulates the efficiency of the coagulation of dust grains -- the first step in planet formation. Within the snow line, where water is vaporised, smaller, rocky planets like our own are believed to form. Outside the water snow line, the presence of water ice allows the rapid formation of cosmic snowballs, which eventually go on to form massive gaseous planets such as Jupiter.