This is the public museum of Harvard's three research museums..and displays over 12,000 specimens, including the reknowned collection of 3,000 'Glass Flowers', flame-worked glass models of flowering plants, amazingly realistic, used to teach botany to students in the 19th and early 20th centuries.  They also display some 5,000 minerals and gemstones, including a 1,642 lb. amethyst geode, and some extraordinary meteorites. Family favorites are the dinosaurs, prehistoric mammals such as glyptodont, giant sloth, a mastodon, as well as over 500 of current day mammals --rhino, hippo, giraffe, three whale skeletons.  New exhibits, such as Evolution and Language of Color, combine video and display specimens from the 21 million in storage behind the scene, and give glimpses of some of the ongoing scientific research at the University.  Definitely worth the 7 minute walk from Harvard Square.