National Institutes of Health-Johns Hopkins University Graduate Partnerships Program 1 article published in JoVE Neuroscience In Vivo Calcium Imaging of Lateral-line Hair Cells in Larval Zebrafish Daria Lukasz1,2, Katie S. Kindt1 1Section on Sensory Cell Development and Function, NIDCD/National Institutes of Health, 2National Institutes of Health-Johns Hopkins University Graduate Partnerships Program The zebrafish is a model system that has many valuable features including optical clarity, rapid external development, and, of particular importance to the field of hearing and balance, externally located sensory hair cells. This article outlines how transgenic zebrafish can be used to assay both hair-cell mechanosensation and presynaptic function in toto.