Electrophysiology provides a unique way of investigating functionality of excitable cells and is vital for understanding brain mechanisms in health and in disease, both in humans and in animal models. Helsinki Electrophysiology platform (HEP) provides state-of-the-art facilities, user training and education in various in vivo and in vitro electrophysiological techniques. Recordings can be made in cell cultures, acute and cultured brain slice preparations as well as in anaesthetized, head-fixed awake and freely-behaving rodents, and can be combined with behavioral tasks, pharmacological and genetic manipulation as well as electrical and optogenetic stimulation.