Fermilab completed the construction and testing of the Neutrino at the Main Injector (NuMI) beam line in early 2005. Protons from Fermilab’s Main Injector accelerator (left) travel 1,000 feet down the beam line, smash into a graphite target and create muon neutrinos. The neutrinos traverse the MINOS near detector, located at the far end of the NuMI complex, and travel straight through the earth to a former iron mine in Soudan, Minnesota, where they cross the MINOS far detector. Some of the neutrinos arrive as electron neutrinos or tau neutrinos.