This book summarizes the emerging experimental evidence and knowledge on hair-cell mechanotransduction. The contents cover its cellular structure, biophysical properties, molecular components and functions. Auditory hair cells convert sound induced vibration into electrical signals, also known as mechanotransduction. This biological process endows us the ability to hear and communicate in our daily lives. However, our understanding of hair-cell mechanotransduction is still far from completion. Recent advance in molecular genetics and biophysics have brought bunches of exciting progress in the field that helped us get deeper insight into this part, especially the molecular constituent and operation of the channel complex. Through this book, we hope to provide a cutting-edge snapshot for our audiences who are interested in or studying how auditory hair cells detect sound.