Metal halide nanocrystals (NCs) have emerged as attractive materials with applications such as displays, solar cells and medical scanners. Even though their potential impact on society is huge, commercialization is hampered by the presence of lead and the instability of the materials against e.g. heat, moisture or light. When developing novel (lead-free) NCs with optimized properties and stability, characterization of the atomic structure and composition is crucial. Transmission electron microscopy (TEM) is an ideal tool, but imaging metal halide NCs by TEM is extremely difficult because of their sensitivity to the electron beam. The goal of this project, which is a unique collaboration between EMAT, the electron microscopy group at the University of Antwerp, and the group of Professor Liberato Manna at IIT (Genova) is therefore to develop innovative TEM methods that will enable us to link the structure and composition of metal halide NCs to their properties and stability. We will hereby exploit the information richness and dose efficiency of a novel technique, called 4D scanning TEM (STEM), and will identify e.g. strain, defects or new phases in metal halide NCs. Moreover, 4D STEM will be combined with in situ TEM holders, which will enable us to investigate atomistic phenomena that occur as a result of environmental triggers. We envisage that our project will lead to the preparation of new generations of NCs with improved properties and stability.