A librarian is a person who works professionally in a library providing access to information, and sometimes social or technical programming, or instruction on information literacy to users. The role of the librarian has changed much over time, with the past century in particular bringing many new media and technologies into play. From the earliest libraries in the ancient world to the modern information hub, there have been keepers and disseminators of the information held in data stores. Roles and responsibilities vary widely depending on the type of library, the specialty of the librarian, and the functions needed to maintain collections and make them available to its users.