Charge/discharge of either Li- and Na-ion batteries in most cases is accompanied by microstructural variations of active materials in the electrodes. These microstructural changes, in turn, have significant impact on cycle life of the batteries. Knowledge of the dynamics of such deformation processes would be valuable to the development of batteries of long cycle-life. The current general understanding on such deformation processes has so far been limited to the dimensional variations. Recent development in operando imaging analytical techniques, such as in-operando transmission electron microscopy and X-ray microscopy (TXM), has offered the opportunities to directly probe the changes in interior microstructures of the active material particles. This talk presents examples of TXM analysis on alloying metal anodes pertaining to Li-ion and Na-ion batteries. Systematical description of the deformation processes for various alloying anode materials reveals complex correlations between their redox kinetics and metallurgical properties, which pave the way for better designed microstructures enabling high-performance anodes for the next generation high-energy batteries.