Nitrous oxide (street name hippy crack, whippets or whippits) is a gas which can induce euphoria, hallucinogenic states and relaxation when inhaled. First recorded in the 18th century at upper-class "laughing gas parties", the experience was largely limited to medical students until the late 20th century when laws limiting access to the gas were loosened to supply dentists and hospitals. By the 2010s, nitrous oxide had become a moderately popular recreational drug in some countries. Possession of nitrous oxide is legal in many countries, although some have criminalised supplying it for recreational purposes.