Col ossal magnetoresistance (CMR) is associated with the phase transition from a metallic ferromagnetic to insulating paramag netic phase, which can be controlled by an applied magnetic fiel d. The insulating phase occurs due to trapping of the charge carriers by polaronic lattice distortions, which raise the resistivity. Theories based on local physics predict that the magnitude of the resistivity jump at T c is determined by how much, on average, the amplitude of these distorti ons increases at the phase transition. Using neutron scattering, we measured the average distortion amplitude in La 0.7 Sr 0.3 MnO 3 . Surprisingly, its increase from below to above T c is just as large as in other mang anites, which have a much l arger resistivity jump. This result suggests that the strength of CMR is determined not by the size of distortions, but by their cooperati ve nature s pecific to each compound. Existing theories need to be extended to include correlations between different unit cells to explain and predict the strength of CMR. Manganese perovskite o xides have a rich temperaturedoping phase diagram spanning a wide range of physical phenomena of both practical and fundamental interest such as metal-insulator transitions, colossal magnetoresistance, mu ltiferro icity, polaron format ion etc. Th is behavior is driven by strong coupling between magnetic, orbital, charge, and atomic lattice degrees of freedo m with ordering in one channel having a strong, often transformational effect on the other. Electron-phonon coupling through the Jahn-Teller effect plays a special role by tying electronic orb ital states to the atomic latt ice whose deformat ions trap charge carriers and thus raise the electrical resistivity. In half-doped manganites the Jahn-Teller effect leads to CE order characterized by very large resistivity, which then drops by several orders of magnitude when the CE order melts at elevated temperatures. At lower doping Jahn-Teller d istortions become frustrated: A distortion in one unit cell interferes with the distortion in the neighboring unit cells and long range CE order cannot form. This part of the phase diagram is famous for its outstandingly large (colossal) magnetoresistance (CM R) [6] , [7]. CM R occurs due to the ferro magnetic transition accompanied by a large resistivity change. The resistivity is metallic-like at temperatures, T, less than the ferro magnetic t ransition temperature, T C , i.e. it is relatively low and increases with T, whereas at T > T C it is very large and typically decreases with T. Due to h igh sensitivity of T C to the applied magnetic field, resistivity changes dramat ically as a function of field in the vicinity of T C . The CM R mechanism itself is straightforward, but what is unusual is the very existence of the "metal-insulator" transition at T C . It has been proposed that the resistivity increases because of competition between double-exchange and Jahn-Teller interactions [8,9]. The former favors ferro magnetism and an undistorted lattice and wins below T C . T...