We have developed high-resolution transmission electron microscopy to study the bimolecular reactions of fullerene and metallofullerene molecules in carbon nanotubes. Fullerene dimerization reactions start from an encounter of two molecules accelerated by phonons, photons, or electrons. The rate of reactions is often discussed from kinetics of the system and dynamics of molecules where the experimental conditions such as pressure, concentration, temperature, and existence of catalysts affect the system. Classic approaches to characterize such behaviors are based on the analysis of thermodynamics, spectroscopy, or microscopy that deal with enormous amounts or assembly of molecules in order to gain enough signal/noise ratios. Scientists have dreamed of capturing the very moment of reactions when the molecules change their structures. We have proved that the atomic resolution imaging of chemical reaction is indeed possible with moderate experimental conditions.