Part 1 Principles of Membrane Potential-Imaging -- Historical Overview and General Methods of Membrane Potential-Imaging -- Design and Use of Organic Voltage-Sensitive Dyes -- Part 2 Membrane Potential Signals with Single Cell Resolution -- Imaging Sub millisecond Membrane Potential Changes from Individual Regions of Single Axons, Dendrites and Spines -- Combining Membrane Potential Imaging with Other Optical Techniques -- Monitoring Spiking Activity of Many Individual Neurons in Invertebrate Ganglia -- Part 3 Monitoring Activity of Networks and Large Neuronal Populations -- Monitoring Integrated Activity of Individual Neurons Using FRET-Based Voltage-Sensitive Dyes -- Monitoring Population Membrane Potential Signals from Neocortex -- Voltage Imaging in the Study of Hippocampal Circuit Function and Plasticity -- Monitoring Population Membrane Potential Signals During Development of The Vertebrate Nervous System -- Imaging the Dynamics Of Mammalian Neocortical Population Activity In-Vivo -- Imaging the Dynamics of Neocortical Population Activity in Behaving and Freely Moving Mammals -- Part 4 Monitoring Membrane Potential in the Heart -- History of Cardiac Optical Imaging -- Imaging of Ventricular Fibrillation and Defibrillation: The Virtual Electrode Hypothesis -- Optical Mapping of Ventricular Fibrillation Dynamics -- Bio photonics Modelling of Cardiac Optical Imaging -- Towards Depth-Resolved Optical Imaging of Cardiac Electrical Activity -- Part 5 New Approaches - Potentials and Limitations -- Two-Photon Excitation of Fluorescent Voltage-Sensitive Dyes: Monitoring Membrane Potential in the Infrared -- Random-Access Multi photon Microscopy for Fast Three-Dimensional Imaging -- High Spatial Resolution Microscopy Using Holographic Illumination -- Second Harmonic Imaging of Membrane Potential -- Genetically Encoded Protein Sensors of Membrane Potential.