Standard ultrasound is already popular in clinical imaging given that it is minimally invasive, low-cost, portable, and can generate images in real time. But until now, it has rarely been used to image the brain. That’s partly because the skull gets in the way—bone tends to scatter ultrasound waves—and the technology is too slow to detect blood flow in the smaller arteries that support most brain function. But a new method of ultrafast ultrasound can trace brain signaling with great precision, d