In 18th-century Europe, revolutionaries such as Philippe Pinel and Johann Christian Reil reformed the hospital system. Instead of the use of metal chains and restraints, their institutions used rigorous work and leisure activities in the late 18th century. This was the Moral Treatment era, developed in Europe during the Age of Enlightenment, where the roots of occupational therapy lie. Although it was thriving in Europe, interest in the reform movement fluctuated in the United States throughout the 19th century. It re-emerged in the early decades of the 20th century as Occupational Therapy.