Circulation's unlikely inception begins with the televised proceedings of the O. J. Simpson criminal trial. Searching for new ideas for REPOhistory projects, I was struck by the way one key piece of evidence, Simpson's blood, was used by both the defense and prosecution. Discovered at the crime scene, dropped into test tubes, and enlarged to disclose its DNA signature, this blood also stood trial. In the process, it revealed itself to be a highly charged symbolic site, as well as the material evidence of forensic science. (There was even a sort of trial within a trial that took place regarding the truth claims of the still emerging field of DNA testing.) More than an oxygen-carrying organ filled with genetic information, Simpson's blood emerged as a specter, haunting the entwined histories of African and European Americans. Intrigued by its complexity, I proposed that REPOhistory, best known for site-specific “repossessions” of lost histories, produce a public art installation about the social history of human blood. The proposal called on artists to map this indispensable fluid along two axes. One follows the economy of human blood as a regulated public resource and multi-billion dollar global industry, disclosing the urban pathway blood travels through Manhattan from donors, to a processing center, and then to hospitals, clinics, and finally waste sites. The other axis pursues the multiple social meanings of human blood, including its aesthetics, folklore, technology, and politics.