Dark field microscopy 

The dark-field signal is sensitive to sample features smaller than the spatial resolution of the sample. By creating an imaging system with a (phase and attenuation) resolution of 1 micron (see Low-energy x-ray microscopy with user-defined resolution below), the dark-field signal becomes sensitive to sub-micron, i.e. nanometric, features while using conventional laboratory equipment, including non-micro-focal x-ray sources.

Differential phase (a) and dark field (b) images of collagen fibres in a cartilage sample, highlighted by red arrows. The fibres are visible in both images, but the signal they generate is different as visible in the plots in (c). While differential phase peaks at the edges of the fibre with alternating bright/dark fringes, dark field peaks at the fibre’s centre, indicating its hierarchical structure. A homogeneous fibre would show comparable differential phase signal, but a flat dark field profile.