Conclusively identifying illness is job one for physicians, who rely on a variety of medical devices, along with an evaluation of signs and symptoms, to determine just what’s ailing patients. Diagnostic tools introduced through the centuries have ranged from microscopes and stethoscopes to thermometers and x-ray imaging and more, which have contributed greatly to modern health care. For good reason, all are still in use and are joined today by new generations of devices incorporating the latest technologies, many of them photonic. Light-based imaging and image analysis are constantly improving, pushed by industry, physicians groups and research organizations. Recently, the first LUNGx Grand Challenge sought quantitative image analysis methods for the diagnostic classification of malignant and benign lung nodules. The event was sponsored by SPIE, the international society for optics and photonics, the American Association of Physicists in Medicine and the U.S. National Cancer Institute. LUNGx culminated in February at the SPIE Medical Imaging 2015 symposium, held in Orlando, Fla., with the evaluation of 13 algorithms from 11 groups. The standout team, led by Lyndsey Pickup, was from Mirada Medical Ltd. of the UK. The runners-up represented the Moffitt Cancer Center at the University of Arizona and were led by Yoganand Balagurunathan. Diagnostic devices are frequent article topics in BioPhotonics, and this issue is no exception. In our cover story, contributing editor Marie Freebody runs a little interference on our path to understanding how optical filters are used to control the spectral content of a light beam for diagnostics. In biophotonics, such filters are essential for testing hemoglobin levels, monitoring blood glucose, detecting infectious diseases and more. Read the feature, “Advances in Optical Filters Provide Rapid, On-the-Go Diagnosis,” beginning on page 18. Also in this issue: “Comparing Micromanipulators for Electrophysiology,” by John Wingerd, of Siskiyou Corporation, beginning on page 22; and, “Focus-Tunable Lenses Enable 3-D Microscopy,” by David Leuenberger, Optotune AG, and Fabian F. Voigt, University of Zurich, beginning on page 26. Enjoy the issue, and then be sure to visit Photonics.com to find news about light and the life sciences, updated daily. While there, you can view the latest Light Matters weekly newscast and watch a growing library of archived webinars, many of which have biophotonics themes. I invite your comments at Karen.Newman@photonics.com.