The number of public sento slowly grew in the 12th Century and their use flourished in the Edo period when, during this peaceful and culturally rich era, with increased economic growth, the baths became as socially vital as they were practical. Providing a space for commoners and the elite to bathe together, the bathhouses were a ground-breaking addition to a deeply hierarchical society. Onsen, which source mineral-rich spring water heated by natural volcanic activity, are the luxurious option for bathers in Japan. Originally reserved for monks during the introduction of Buddhism in 6th-Century Japan, the baths were eventually opened to the public, albeit initially only to the ill and the wealthy. When bathing, however, the seemingly simple gesture of removing your clothes serves to remove your societal position, albeit temporarily. While the natural hot springs known as onsen are familiar worldwide, and can be private or public, there are also the lesser-known sento — public baths relying on regular, filtered water. Often claiming a myriad of restorative properties, from purifying skin to easing arthritis, they are regularly cited in legends as healing animals and ancient gods. Their importance as lively community gathering spaces is colourfully depicted in Edo- and Meiji-era ukiyo-e woodblock prints of idyllic and playful scenes in everyday life.