Universidad de la Plata and Conicet 1 article published in JoVE Biology Local Field Fluorescence Microscopy: Imaging Cellular Signals in Intact Hearts Yuriana Aguilar-Sanchez*1, Diego Fainstein*2,3, Rafael Mejia-Alvarez4, Ariel L. Escobar5 1School of Natural Sciences, University of California, Merced, 2Centro de Investigaciones Cardiovasculares, Universidad de la Plata and Conicet, 3Facultad de Ingenieria, Universidad Nacional de Entre Rios, 4Department of Physiology, Midwestern University, 5School of Engineering, University of California, Merced In the heart, molecular events coordinate the electrical and contractile function of the organ. A set of local field fluorescence microscopy techniques presented here enables the recording of cellular variables in intact hearts. Identifying mechanisms defining the cardiac function is critical in understanding how the heart works under pathological situations.