Hybrid organic-inorganic metal halide perovskites are highly favourable materials for efficient photovoltaic and optoelectronic applications. The mechanisms behind their impressive performance have yet to be fully understood, but they likely depend on atomic level properties that may be unique to these perovskites. Atomic-resolution transmission electron microscopy is well suited to provide new insights but is challenging because of the highly beam-sensitive nature of hybrid perovskites. In a recent paper published in Science we report on an approach based on scanning transmission electron microscopy (STEM) that does now allow atomic-resolution imaging. Through measurements of the atomic structure and the local chemical composition of crystalline defects, such as grain boundaries and stacking faults, we aim to understand the influence of these defects on photovoltaic and optoelectronic performance. Making this link provides a rational basis for further optimising these devices leading to higher efficiencies. This project would suit a student interested in a student seeking a range of experiences including sample synthesis and preparation, operation of world-leading electron microscopes, understanding image formation and interpreting spectroscopic data, data processing and quantification, and understanding how defects affect bonding and electronic structure and relating that understanding to properties.