In-situ neutron and synchrotron X-ray diffraction deliver unique and complementary insight into the microstructural evolution of metals at high temperature, during thermo- mechanical processing or under high pressure. Neutrons illuminate a larger bulk volume and reveal quantitative phase abundance, bulk texture, lattice parameter changes and other ensemble averaged quantities. They are particularly sensitive to characterize atomic order and disorder in titanium aluminides. In contrast, fine- bundled synchrotron high-energy X-rays deliver reflections from a number of individual grains. For each constituting phase, their statistics and behavior in time reveal information about grain growth or refinement, subgrain formation, static and dynamic recovery and recrystallization, slip systems, twinning, etc. Grain orientation correlation can be revealed and lattice strain gives complementary insight to the transformation and reaction processes. This presentation reviews pioneering experiments on metallic and intermetallic systems in reciprocal space, which nowadays serve the wider community.