Based on the mature development of microfabrication technology, micro-scale electrodes, i.e., microelectrodes, for the electrical observation of activities in micro-scale environment become realisable. This technique opened a new avenue for micro-scale observation and measurement besides the optical technique. This book presents the techniques, structures, and applications of using microelectrodes in a micro-scale environment. It covers a broad spectrum of topics and the state of the art techniques in the field. As such, the book is divided into four sections, comprising 11 chapters written by recognised experts from leading groups around the world. The reader will gain a unique perspective on the challenges and emerging opportunities in the technology of microelectrodes.