English: High resolution x-ray image of a spider. The phase-contrast technique provides much higher contrast than normal absorption-contrast x-ray imaging, making it possible to see smaller details. It has become an important method for visualizing cellular and histological structures in a wide range of biological and medical studies. There are several technologies being used for x-ray phase-contrast imaging, all utilizing different principles to convert phase variations in the x-rays emerging from an object into intensity variations. These include propagation-based phase contrast, Talbot interferometry, refraction-enhanced imaging, and x-ray interferometry. Phase contrast requires an x-ray source that can generate very small and very bright focal spots. In the case shown here, the source is a metal-jet-anode microfocus x-ray tube, where the solid metal anode of a normal tube is replaced with a jet of liquid metal. This allows extremely high power density (>500 kW/mm²) and extremely small focal spots (5-30 µm).