A team of researchers in the U.S. has developed a new tool that images blood flow through blood capillaries. Called spectral contrast optical coherence tomography angiography (SC-OCTA), the 3D-imaging technique can detect subtle changes in capillary organisation for early diagnosis of disease. More than 40 billion capillaries, which are tiny, hair-like blood vessels, are tasked with carrying oxygen and nutrients to the far reaches of the human body. But despite their sheer number and monumental importance to basic functions and metabolism, not much is known about their inner workings. The achievement is part of increasing technological advances that allow smaller and smaller blood vessels to be imaged and provide more comprehensive, functional information. The technology allows the measurement of blood flow, oxygenation and metabolic rate. The paper was published last week in the journal Light: Science and Applications.