SAN DIEGO, CA--Commonly, we think of cancer as anarchy, a leaderless mob of deranged cells, storming through the body. Pedro Lowenstein, Sebastien Motsch, and colleagues at the University of Michigan and University of Arizona think that cancer is highly organized--self-organized. In brain cancer, the Michigan and Arizona researchers report that glioma cells build tumors by self-organizing into streams,10-20 cells wide, that obey a mathematically predicted pattern for autonomous agents flowing together.