Lava Lamps, invented by a British accountant Edward Craven Walker in 1968 who t hen set up a company ‘Mathmos’ to sell and distribute them. Still going today in the original factory in Poole, Dorset.
Interesting factoid:- In 2004, a man from Kent,Washington,USA was killed by a lava lamp on a kitchen stove while closely observing it from only a few feet away. Heat from the stove built up pressure in the lamp until it exploded and a shard pierced his heart, causing fatal injuries. Probably won the Darwin Award that year 🙂
Oldies but still going strong!