The permanent collection of the foundation is based primarily on nine private collections: Solomon R. Guggenheim's collection of non-objective paintings; Karl Nierendorf's collection of German expressionism and early abstract expressionism; Katherine S. Dreier's gift of paintings and sculptures; Peggy Guggenheim's collection, concentrating on abstraction and surrealism; Justin K. and Hilde Thannhauser's collection of impressionist, post-impressionist, and early modern masterpieces; part of Hilla von Rebay's collection; Giuseppe Panza di Biumo's holdings of American minimalist, post-minimalist, environmental and conceptual art of the 1960s and 1970s; a collection of photographs and mixed media from the Robert Mapplethorpe Foundation; and the Bohen Foundation's collection of film, video, photography and new media. The foundation's collections have expanded greatly through eight decades and include every major movement of 20th- and 21st-century art. Its directors and curators have attempted to form a single collection that is not encyclopedic, but rather based on their unique visions. The collection has grown in scope to include new media and performance art, and the foundation has entered into collaborations with YouTube and BMW.