Developing materials for optical and electrical applications often requires an understanding of the relationships between processing and point defects. Atomic scale relationships such as these are frequently elusive to understand due to a lack of characterization techniques. In this work, I will show examples of nanoscale and atomic scale characterization of oxide and semiconductor point defects determined through atom probe tomography (APT). Specifically, oxygen stoichiometries in oxygen and proton conducting oxides can be directly related to the electrical conductivities where grain boundaries dominate transport. Laser assisted APT also allows for unique opportunities for measuring atomic diffusion where thermal transport can assist transformations from metastable states. Using a “Dynamic” atom probe, atomic scale diffusion can be quantified at the atomic scale in 3-dimensions using a combination of APT and in-situ electron diffraction with a temporal resolution of better than 1 ns. An in-situ STEM / APT instrument engineered and constructed at CSM will be detailed as well as opportunities for using such data for improved APT data reconstruction.