The introduction of performance within the museum has led to radical changes in documentation, conservation and exhibition practices. Depending on where documentation is placed within the museum, documentation can be a record (in the archive), an exhibit (in the collection) or a mode of engagement (on social media). It is through documentation that museums orchestrate the historicization, value creation and spectacle of art. These findings about documentation show that artworks must no longer be considered purely as objects, or even as processes, but rather as instances in a rhizomatic assemblage of relational and contextual trajectories. Using case studies from Tate, the San Francisco Museum of Modern Art, MoMA and LIMA, and analysing the evolving role that documentation has played in these museums in the period from the 1970s to today, this chapter shows that whether as a remain, ontological evidence, a preservation method, an art exhibit or even a strategy for reinterpretation, the assemblage of documentation constitutes one of the most complex and dynamic fields of inquiry in the late twentieth and early twenty-first centuries.