In Cold War-era “Stranger Things,” we see Eleven, a girl with psychokinetic abilities, in an isolation tank as Dr. Martin Brenner prepares to have her attempt to intercept communication with Russian officials. However, she inadvertently contacts interdimensional entities instead. While in the tank, Eleven may be terrified, but you shouldn’t be – in real life, isolation tanks are used to imbue the user with a sense of weightlessness and relaxation.

Isolation tanks, also known as sensory deprivation tanks, are light-deprived and sound-resistant tanks filled with Epsom salt water at skin temperature. While users float on their backs in purified salt water, they experience the sensation of sensory deprivation, or near-complete deprivation of environmental stimuli. Isolation tanks were first used in 1954 by John Cunningham Lilly to study the brain’s reaction when denied “external stimulation” in order to conduct research on the nature of consciousness.