Breast cancer will strike more than 200,000 women in the United States this year, and 40,000 will die. X-ray mammography is the best way to detect early tumors, but the technique misses one in five cases, and women find the test uncomfortable. Susan Hagness and collaborators have invented a better breast-imaging technique. A woman lies on her back so that her breasts flatten naturally, and an instrument Hagness is developing scans the breast tissue with very-low-power microwaves, which are safer than x-rays. Hagness’s preliminary measurements on breast biopsy specimens indicate that microwave imaging makes malignant tumors stand out better than x-rays do. The energetic Hagness developed sophisticated computer algorithms—which process data collected by the imaging instrument—to enhance the detection and discrimination capabilities of microwave imaging. So far, her computational studies indicate that her approach should detect tumors just a couple of millimeters across, an improvement on the five-millimeter limit of x-ray mammography. The first version of Hagness’s instrument will be used for research.