This book covers the full scope of biochemical sensors and offers a survey of the principles, design and applications of the most popular types of biosensing devices. It is presented in 19 chapters, written by 20 distinguished scientists as well as their co-workers. The topics include the design of signal transducers, signal tags and signal amplification strategies, the structure of biosensing interfaces with new biorecognition elements such as aptamers and DNAzymes, and different newly emerging nanomaterials such as Au nanoclusters, carbon nitride, silicon, upconversion nanoparticles and two-dimensional materials, and the applications in wearable detections, biofuel cells, biomarker analyses, bioimaging, single cell analysis and in vivo sensing. By discussing recent advances, it is hoped this book will bridge the common gap between research literature and standard textbooks. Research into biochemical sensors and their biomedical applications is proceeding in a number of exciting directions, as reflected by the content. This book is published in honor of the 90th birthday of Professor Shaojun Dong, who performed many pioneering studies on modified electrodes and biochemical biosensors.