This department is composed of special collection which cam be defined as a group of items, such as rare books or documents, that are either irreplaceable or unusually rare and valuable. For this reason special collections are stored separately from the regular library collections in a secure location with environmental controls to preserve the items for posterity. Special collections also include rare items that are focused on a single topic, such as aviation or women’s history. Special collections are created to benefit scholars by grouping related materials together in one repository. Often a repository will specialize in a limited number of subject areas for their special collections, to distinguish the institution from other libraries.