Museums of natural history play a significant role in interpreting the natural world in scientific terms. They are sites where initially taxonomic, then geographic, and more recently environmental emphases have been reflected in their holdings and displays. Several issues frame their history: what individual museums hold; how objects are acquired; which material artifacts are displayed and in what arrangement; what audience observes them and for what purposes; and who sponsors museum activities. Cultural historians are particularly interested in museums as places that elaborate meaning through material objects on display, paying particular attention when interpretation is contested. Museum historians have traced the work of curators who developed and extended systematics within the natural sciences.