Gizmodo described the process of plopping a GoPro into a lava lamp is “akin to peering inside a beating human heart as blood cells swirl all around you.” But it might be even more similar to looking inside the melting heart of a wax sculpture. McGill University explains that the classic lava lamp — which was invented in 1963 by British accountant Edward Craven-Walker — primarily contained blobs of paraffin wax combined “with compounds like carbon tetrachloride added to increase its density.” The wax sits in water or mineral oil, “with dyes and sparkles added for whimsy.”

Switching on the lamp causes the wax to rise and fall. That’s because the heat from the bulb causes the wax to expand, reducing its density and allowing it to float. Floating increases the wax’s distance from the heat source, causing it to cool off, become denser and sink. The coolest part of all this is that the basic principle is so simple that you can build your own lava lamp.