The purpose of this proposal is to study unexplained 3D damage progression in novel hybrid nano/microfiber hierarchical advanced composites, featuring aligned nanofibers in two different configurations: (i) nanostitch, and (ii) newly designed nanostitch 2.0 with even higher CNT volume fraction. With the recent EBS upgrade enabling an expansive test matrix, synchrotron radiation computed tomography will be used to visualize and analyze in situ damage nucleation and progression to support the establishment of fundamental relationships between diverse, unexplored damage precursors (i.e., morphological features that nucleate or alter damage progression) and the complex failure mechanisms exhibited in aerospace-grade carbon microfiber reinforced plastics. The generated data will also support the development of seminal artificial intelligence-driven automated morphology and damage segmentation tools and, consequently, accelerate all future studies of 4D damage in heterogeneous materials.