ERthermAC staining in primary myocytes. Representative images of bright-field (top left), and fluorescence images of WT primary myocytes co-stained with Cal-520 (bottom left) and the SR/ER-targeted fluorescent molecular thermometer ERthermAC (bottom right). Merged image is shown on the top right. Cal-520 was excited at 480 ± 9 nm, and fluorescence was imaged at 520 ± 14 nm. ERthermAC was excited at 556 ± 10 nm, and fluorescence was imaged at 617 ± 37 nm.