Guided tours serve as a bridge between exhibits and visitors and, Museum-trained volunteers or docents introduce visitors to National Museum of Natural Science and its collection. For the biennium 2003-2004, in addition to taking reservations for guided tours from schools and organizations in general, information desks in the Museum also offered interpretive services if manpower permits. Guided tours can be adapted according to the nature and purpose of visit, giving visitors a specific, thorough interpretation within their schedule. Usually a guided tour lasts about half an hour, and any school or organization in general of over 20 people may make a reservation in advance.