Topics of in-situ transmission electron microscopy studies on the dynamic behaviors of materials are described. Estimation of the activation energy for the migration of self-interstitial atoms is successfully carried out. The coalescence between nm-scale prismatic dislocation loops with different Burgers vectors, as well as the one-dimensional glide diffusion of the loops, has been confirmed. A new electron-beam-induced deposition method using no precursor gas, has been developed for the fabrication of tungsten nanostructures. Size dependence of the eutectic temperature of alloy particles was examined. A linear relationship between the eutectic temperature and the inverse radius of the particle was obtained. In-situ experiments with TEM are useful in revealing the dynamic behaviors of materials.