This article is based on the award lecture of the Japan Society of Calorimetry and Thermal Analysis (JSCTA) Award in 2022. Neutron scattering is a powerful experimental technique which is comprehensive with calorimetry. For the last 20 years, my group has carried out both adiabatic calorimetric and various neutron scattering experiments for the studies of various complex condensed systems. In the adiabatic calorimetry, the measurements of heat capacity and enthalpy of absorption have been carried out. In the neutron scattering, powder diffraction, inelastic scattering, and quasielastic scattering techniques have been utilized, each providing structural, vibrational/rotational excitation and relaxational information. The basic knowledge of neutron scattering and its complementarity with thermal measurements are described in the first part of the article. Then, as the examples, the hydrogen absorption and interstitial-sites occupation in palladium nanocrystals, low-energy excitations (boson peaks) in vapor-deposited simple molecular glasses, and diffusion dynamics of MOF (Metal-Organic Frameworks) based proton conductors, and intramolecular dynamics of high-entropy liquids are described along with instruments used in their experiments.