Property is a central social institution, posing fundamental questions about efficiency and fairness that are mediated through the legal system. What can we own? To what extent can government regulate what we own? When can government "take" from us? Anglo-American property law developed in the context of land, governing the transmission to succeeding generations of wealth and status. Today's questions (ownership of music, control of body parts and of endangered species, rights to spectrum) apply traditional legal concepts and show their evolution.