Lava lamps (or astro lamps) are decorative novelties, invented by British accountant Edward Craven-Walker in 1963. The lamps contain blobs of colored wax inside a glass vessel filled with clear liquid. The wax rises and falls as its density changes from the heat of an incandescent bulb underneath the vessel. The appearance of the wax resembles pahoehoe lava.
Craven-Walker was inspired by watching a homemade egg timer made out of a cocktail shaker filled with liquids bubbling on a stove top at a pub. The lamps became all the rage through the late 60s and 70s.
In the early 90s, Craven-Walker took on a business partner called Cressida Granger. In 1992, they changed the company name to Mathmos. They continue to make authentic Lava Lamps in the original Poole, Dorset, UK factory where Craven-Walker first set up shop in 1968.