Rapid, self-sustaining thermochemical reactions of reactive materials are not well understood at molecular/atomic levels, regarding how they evolve chemically and release energy at high temperatures. This situation emphasizes the need of real-time structural and temperature data obtained during thermochemical reactions in reactive materials. In this paper, we describe time-and angle-resolved x-ray diffraction (TARXD) capable of probing the structural and temperature evolution of reactive materials upon thermal ignitions using pulse laser-and electric-heating. Several types of reactive materials were investigated to elucidate chemical mechanisms for: (i) intermetallic exchange reactions in Al/Ni(50:50) to Al3Ni2 and Al3Ni, upon rapid quenching of molten phases of Al/Ni alloys; (ii) diffusion-controlled, solid-state combustion reactions in intermetallic composites of (Al/Ni(50:50)+h-BN) and metallic composites (Al + h-BN) to produce h-AlN; and (iii) combustion reactions of metallic mixtures (Al + B) with N-2 in air to produce metastable cubic AlN. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.