In OPN’s December “Optics in 2020” review of interesting research, Marcel Schubert and Malte Gather described recent studies that used spherical whispering-gallery-mode, bio-compatible microlasers to analyze heart muscle cells (cardiomyocytes) in live animals, leveraging the sensitivity of microlasers to local changes in refractive index. The team was able to use the lasers to extract transient profiles of cardiomyocyte contractility in their immediate environment.