Nitrous oxide
Nitrous oxide gas produces euphoriant effects when inhaled. First recorded in the 18th century at upper-class "laughing gas parties", the experience was largely constrained 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.