AbstractNeedle‐type voltammetric ultramicroelectrodes show exceptional sensitivity for the detection of redox‐active substances, rapid response times, and total tip diameters in the lower micrometer range. These characteristics make them ideal for analyzing the chemical environment and the activity of isolated living cells, which in their various forms are the microscopic building blocks of human, animal, and other life forms. Prerequisites for successful local electrochemical measurements in the vicinity of the tiny biological objects are gentle, stress‐free, and accurate placement of the tip at the cell, exact knowledge of the tip‐to‐cell distance, and appropriate selectivity of the ultramicroelectrode tip for species that may change in concentration as a result of cellular actions such as growth, respiration, or transmitter and metabolite uptake or release. The concepts of single‐cell microelectrochemistry are considered and an overview is given of recent results on the fundamental mechanisms of cell functions.