American Museum of Natural History, institute established in New York City in 1869. It is a major centre of research and education on the natural sciences. It pioneered in mounting field expeditions and in creating dioramas and other lifelike exhibits showing natural habitats and their plant and animal life. The museum’s collections of research specimens number more than 30 million, and its collections of fossils and of insects are among the largest in the world. Its exhibits of fossil dinosaurs and mammals are particularly impressive. The museum conducts research in anthropology, astronomy, entomology, herpetology, ichthyology, invertebrates, mammalogy, mineralogy, ornithology, and vertebrate paleontology. The museum has a 485,000-volume library on natural history, as well as photo, film, and manuscript collections. It also conducts a wide range of educational activities for the public and publishes the monthly magazine Natural History. The Hayden Planetarium, one of the world’s largest, forms part of the museum; it has a 10,000-volume library on astronomy and a 75-foot- (23-meter) diameter Sky Theater.