This segment demonstrates how cancer spreads through a mechanism called metastases, and how the puzzle of metastases inspired Dr. Folkman to identify more angiogenesis inhibitors. This is Part 6 of a 8 part series (http://www.pbs.org/wgbh/nova/cancer/program.html) that introduces a possible non-toxic cancer treatment and highlights the long journey of how angiogenesis (new blood vessel growth) was discovered, how most scientists thought angiogenesis as ridiculous, how angiogenesis was proven existed and crucial to tumor growth, and the effort of searching angiogenesis inhibitors. This series not only shows scientists' problem-solving in research laboratory, but also shows how scientists face the harsh critics/examines from their peers. Moreover, this series shows even though the logic of an experimental design could be very simple, it often takes many years of hard work to identify the target of interest. Biotechnologies such as protein purification and cell cultures are shown in this series.