Schematics of the iterative projection image registration workflow for nanoscale X-ray tomographic reconstructions. Step a is the initial tomographic reconstruction without registration of the projection images. Step b is the reprojection of the 3D matrix in different viewing angles. Step c is the registration of the raw data to the reprojected images. As indicated in the inset, several registration algorithms were implemented to conduct step c. Step d is the tomographic reconstruction of the registered images. Several tomographic reconstruction algorithms are also implemented for this step as well.