Up until now, scientists could only calculate the mass of large groups of molecules, by ionizing them (giving them an electric charge) and then seeing how strongly they interacted with an electromagnetic field, a technique known as mass spectrometry. They had no way, however, of measuring the mass of a single molecule. This has now changed with Caltech scientists have created an ultra-sensitive device that can weigh an individual molecule for the first time. By weighing each molecule, they were able to determine exactly which kind of IgM it was, hinting at potential future medical applications. The initial demonstration weighed a immunoglobulin M, or IgM molecule hinting at future medical applications. A kind of cancer known as Waldenström macroglobulinemia, for instance, is reflected by a particular ratio of IgM molecules in a patient’s blood, so future instruments building on this principle could monitor blood to detect antibody imbalances indicative of cancer. Click on the image or title to learn more.