Functional nanomaterials experience dynamic physical and chemical changes during the operating cycles, which can potentially degrade the performance. In situ transmission electron microscopy (TEM) reveals the dynamic of the materials leading to the establishment of structure-property-performance relationships to optimize the material's design. In this work, we introduce an investigation of nanomaterials dynamics using in situ TEM coupled with a combination of external stimuli in heterogeneous phase environments to mimic the operating conditions of functional materials. First, the simultaneous acquisition of 2D projection and 3D topographic imaging in an environmental TEM (ETEM) setup is developed to analyze the structure dynamics of supported catalytic nanoparticles during heating and gas exposure. Next, we introduce the in situ TEM characterization of the nanomaterials dynamics in controlled liquid environments. Functional nanomaterials are often operated at elevated temperatures under electrochemically cycling conditions. Therefore, heating and biasing should be implemented simultaneously in in situ TEM to image the nanomaterials in their operating conditions. We introduce the temperature effect on the chemical environment of liquid and corresponding nanocrystal growth under electron beam-induced radiolysis in liquid cell TEM. Finally, we develop liquid cell TEM with simultaneous control of temperature and electrochemistry. This work shows that in situ TEM, coupled with a quantitative understanding of the physical and chemical environments, can provide insights into the nanostructure dynamics for understanding the degradation mechanisms of functional materials.