Designs programmable DNA nanodevices as quantitative fluorescent reporters to map second messengers in real time inside specific organelles of living cells. Research directions: (1) DNA origami ion-sensing nanodevices for pH, Cl-, Ca2+, HOCl, and membrane voltage with single-organelle addressability; (2) targeting nanodevices to endosomes, lysosomes, mitochondria, and ER to dissect organelle biology and disease mechanisms; (3) in vivo deployment in C. elegans and Drosophila. NIH Director's Pioneer Award 2022.