This project aims at gaining novel insight in two pathological mechanisms observed in the vascular system supplying the heart and brain of COVID-19 patients as an adverse consequence of a SARS-CoV-2 infection, i.e. the development of 1) macroscopic thrombi (MTs) in epicardial coronary and carotid arteries and 2) peripheral microscopic thrombi (µTs) in myocardial and brain microvasculature. Few pathology studies have been conducted thus far and a precise mechanistic understanding is still needed. We propose the use of a combination of different synchrotron analysis techniques (X-ray micro- & nano-CT, fluorescence & SAXS/WAXS) for the characterization of the morphology, composition and structure of the MTs and µTs. In this specific experiment, we will apply X-ray nano-holotomography and fluorescence microscopy to obtain an unprecedented morphological and chemical characterization of the MTs and µTs at the level of individual thrombi, endothelial cells and possibly SARS-CoV-2 virions.