Requiring just a drop of blood, American researchers have designed a microfluidic assay that can diagnose sepsis, a life-threatening condition responsible for 250,000 deaths annually in the US. By using a new microfluidic device to measure the motility of neutrophils, the most common type of white blood cells in humans, and applying a machine learning algorithm, they were able to diagnose sepsis with 97% sensitivity and 98% specificity (Nature Biomed. Eng. 2 207).