The increasing complexity of nanodevices requires multiscale 3D characterization techniques spanning from the nanometer to the atomic scale. STEM-EDX tomography provides three-dimensional elemental mapping at the nanometer scale. Recent deep learning-based approaches have achieved near-isotropic spatial resolution of approximately 5 nm in specimens 60–100 nm thick. Electron ptychography offers complementary capabilities for atomic-resolution structural characterization. This PhD aims to develop a correlative methodology combining both techniques on the same specimen. STEM-EDX tomography will first be performed on relatively thick TEM lamellae. The specimens will subsequently be thinned to a target thickness below 30 nm for 4D-STEM acquisition. Multislice electron ptychography will provide depth-resolved structural information. Simulations will be used to optimize experimental conditions and acquisition parameters. EDX spectral processing and limited-angle tomographic reconstruction methods will be optimized. Ptychographic reconstruction algorithms will be evaluated in terms of resolution, robustness, and sensitivity to light elements. A major challenge will be the spatial registration of chemical and structural volumes before and after specimen thinning. Reconstruction accuracy and limitations will be assessed using simulations and reference specimens. The methodology will be applied to phase-change memory (PCM) devices and InGaN-based nano-emitters. The ultimate goal is to establish a correlative 3D characterization approach linking chemical composition, atomic structure, and nanodevice properties.