What Bimetallic nanoparticles composed of two different metals show unique properties compared to their monometallic counterpart. In this project, I will investigate the 3D structures of bimetallic nanoparticles in real-time under operando conditions by combining state-of-the-art quantitative transmission electron microscopy (TEM) and high-pressure gas cells. I aim to obtain a fundamental understanding of the dynamic evolution and redox mechanisms of bimetallic nanoparticles under realistic reaction conditions, as well as morphological and chemical transformations. I will develop a chemically sensitive 3D characterisation method with a spatial resolution from micrometre down to the atomic level. Why When the scale of materials down to 1-100 nanometers, the materials' properties change significantly. The generic understanding of the synergistic effect (size effect + alloying effect) is still unclear hindering the nanotechnology engineering based on such materials. In addition, the behaviour of the nanoparticles under working conditions is completely different from those observed under high vacuum conditions. The dynamic changes of the nanoparticles during reaction or pre-treatment procedures is poorly understood. Therefore, atomistic chemical sensitive 3D investigations under realistic conditions of such systems can add valuable information, both from a fundamental science perspective as well as a technological point of view. How This project will be carried out at DTU Nanolab and the DNRF VISION centre at DTU physics, which host unique TEM characterization platform, including environmental TEM (ETEM) and a high-pressure gas cells for real-time imaging of atomic morphology evolution under in situ and operando conditions. The experiment for chemically sensitive 3D characterisation will be conducted ex situ in a TEM equipped with an advanced fast EDX detector. Open source software such as MULTEM is used for image simulation, StatSTEM for image quantification, ASTRA toolbox for 3D reconstruction, and OVITO for 3D model visualization. The sample nanoparticles with well-defined size and stoichiometric ratio of two elements will be supplied by SURFCAT at DTU Physics. SSR This project intends to utilize the existing instrumentation at DTU for operando characterisation and chemical sensitive 3D characterisation for alloy nanoparticles. The developed methods open way to investigate functional alloy nanoparticles, such as catalytic nanoparticles, quantum dots, fluorescence nanoparticles, bio-sensing nanoparticles, etc. under their operating conditions. The advances in characterization techniques will benefit both research groups and industrial companies interested in catalysis and functional materials developments.