Battery Breakdown: Although a range of materials can be used for chemically storing electrical charge, many cannot be made into batteries that retain their capacity over many cycles. Failure may be because of secondary reactions, poisoning through the formation of surface coatings, or volumetric changes leading to fracture. Ebner et al. (p. 716 , published online 17 October) studied this last scenario in an operating battery using synchrotron x-ray tomographic microscopy, tracking both the chemical changes in the battery and the resulting mechanical changes in a tin oxide model system, which is known to undergo large volume changes.