Experimental condensed matter physics uses neutrons as probes to study strongly correlated electron systems. The microscopic origin of high-transition temperature (Tc) superconductivity, magnetism and electron-lattice coupling in high-Tc superconductors. Magnetism and lattice effects in colossal magnetoresistance (CMR) manganese oxides. Quantum criticality in Ru-based oxide materials and other transitional metal oxides. Our work is supported by the National Science Foundation and the Department of Energy.