A digital library, also called an online library, an internet library, a digital repository, a library without walls, or a digital collection is an online database of digital objects that can include text, still images, audio, video, digital documents, or other digital media formats or a library accessible through the internet. Objects can consist of digitized content like print or photographs, as well as originally produced digital content like word processor files or social media posts. In addition to storing content, digital libraries provide means for organizing, searching, and retrieving the content contained in the collection. Digital libraries can vary immensely in size and scope, and can be maintained by individuals or organizations. The digital content may be stored locally, or accessed remotely via computer networks. These information retrieval systems are able to exchange information with each other through interoperability and sustainability. The early history of digital libraries is not well documented, but several key thinkers are connected to the emergence of the concept. Predecessors include Paul Otlet and Henri La Fontaine's Mundaneum, an attempt begun in 1895 to gather and systematically catalogue the world's knowledge, with the hope of bringing about world peace. The visions of the digital library were largely realized a century later during the great expansion of the Internet. Vannevar Bush and J.C.R. Licklider are two contributors that advanced this idea into then current technology. Bush had supported research that led to the bomb that was dropped on Hiroshima. After seeing the disaster, he wanted to create a machine that would show how technology can lead to understanding instead of destruction. This machine would include a desk with two screens, switches and buttons, and a keyboard. He named this the "Memex". This way individuals would be able to access stored books and files at a rapid speed. In 1956, Ford Foundation funded Licklider to analyze how libraries could be improved with technology.