Frog olfactory bulb neurons labeled with fluo-3 (Cat. no. F1240, F3715) and Fura Red™ (Cat. no. F14219) Ca²⁺ indicators, demonstrating a Ca²⁺ response to treatment with KCl and nifedipine. (J Physiol 487, 305 (1995)) The image is a ratio of fluo-3 and Fura Red™ fluorescence images acquired with a Leica confocal laser-scanning microscope. The image was contributed by J. Bischofberger and D. Schild, Physiology Institute, University of Göttingen.