Children's museums are institutions that provide exhibits and programs to stimulate informal learning experiences for children. In contrast with traditional museums that typically have a hands-off policy regarding exhibits, children's museums feature interactive exhibits that are designed to be manipulated by children. The theory behind such exhibits is that activity can be as educational as instruction, especially in early childhood. Most children's museums are nonprofit organizations, and many are run by volunteers or by very small professional staffs. International professional organizations of children's museums include the Association of Children's Museums (ACM), which was formed in 1962 as the American Association of Youth Museums (AAYM) and in 2007 counted 341 member institutions in 23 countries, and The Hands On! Europe Association of Children's Museum (HO!E), established in 1994, with member institutions in 34 countries as of 2007. Many museums that are members of ACM offer reciprocal memberships, allowing members of one museum to visit all the others for free or for a discounted fee. History The Brooklyn Children's Museum was established in 1899 by the Brooklyn Institute of Arts and Sciences. It is often regarded as the first children's museum in the United States. The idea behind the Brooklyn Children's Museum implicitly acknowledged that existing American museums were not designed with children in mind. Although museums at the turn of the century viewed themselves as institutions of public education, their exhibits were often not made accessible for children, who may have struggled with simple design features like the height of exhibit cases, or the language of interpretive labels. Furthermore, touching objects was often prohibited, limiting visitors' ability to interact with museum objects. The founders of the Brooklyn Children's Museum were concerned with education and realized that no other institution had attempted to establish "a Museum that will be of especial value and interest to young people between the ages of six and twenty years". Their goal was to gain children's interest and "to stimulate their powers of observation and reflection" as well as to "illustrate by collections of pictures, cartoons, charts, models, maps and so on, each of the important branches of knowledge which is taught in elementary schools". Anna Billings Gallup, the museum's curator from 1904 to 1937, encouraged a learning technique that allowed children to "discover" information by themselves through touching and examining objects. Visitors to the museum were able to compare the composition, weight, and hardness of minerals,