Waiting for a specific atom of a radioactive element to undergo nuclear transmutation could be futile because those events happen randomly. Yet a research team led by Tufts University chemist E. Charles H. Sykes has observed individual atoms of 125I transmuting to 125Te (Nat. Mater. 2015, DOI: 10.1038/nmat4323). The study deepens understanding of electron emission processes and may lead to new ways to study the effects of ionizing radiation on biological tissues and new approaches to cancer therapy. To observe the nuclear events, the team prepared monolayer films of radioactive 125I on gold-coated mica. By analyzing the films for months with X-ray photoelectron spectroscopy and scanning tunneling microscopy, the team observed the initially tellurium-free samples become enriched in tellurium and observed the telltale signs of individual iodine atoms undergoing nuclear decay. The researchers note that as 125I atoms decay, they emit electrons that stimulate emission of many additional low-energy electrons that are reflected from the gold surface. By binding 125I to gold nanoparticles and attaching the particles to antibodies or other compounds that target tumors, these low-energy electrons, which effectively rupture cancer cells’ DNA, could improve the efficacy of cancer therapies, the team suggests.