Amongst the museums of ancient times, mention must be made of the Museaum (institute) for philosophy and research in Alexandria, founded by Ptolemy I Soter (about 280 BC) and that of Plato in Athens (350 BC). Early museums began as the private collections of wealthy individuals, families or institutions. These were often displayed in so-called wonder rooms or cabinets of curiosities. The first public museums in the world opened in Europe during the 18th century and the Age of Enlightenment. Today the official definition of a museum is "permanent institution in the service of society and of its development, open to the public, which acquires, conserves, researches, communicates and exhibits the tangible and intangible heritage of humanity and its environment, for the purposes of education, study, and enjoyment".