This lecture covers the principles of electrical stimulation of tissues, including the equivalent circuit model, neuron stimulation mechanisms, charge injection mechanisms, and the effects of electrode capacitance. It explains the importance of biphasic pulses, conductive polymer coatings, and charge-balanced waveforms to prevent tissue damage. The lecture also discusses the limitations of different materials for charge injection, such as platinum and iridium oxide, and the impact of electrode damage on stimulation efficiency.