In this podcast episode, MRS Bulletin’s Laura Leay interviews PhD candidate Laura Albero Blanquer and her professor, Jean-Marie Tarascon, from the Collège de France in Paris about their study on what occurs inside the cells of both liquid and solid-state batteries. They embedded the optical Fiber Bragg grating sensor that reflects monochromatic light, revealing a shift in the peak wavelength when there is a change in temperature, pressure, or stress. The sensors were calibrated so that only changes in stress could be detected. This research will lead to new opportunities to look at commercial liquid cells, and to greater insight into the chemo-mechanical processes in electrodes and in all solid-state batteries, which could lead to enhanced performance. Their study is published in Nature Communications (https://doi.org/10.1038/s41467-022-28792-w).