This book is intended as a textbook that presents a modern approach to radiation dosimetry, covering the principles and applications of microdosimetry in radiation dosimetry, radiation protection, radiation biophysics and radiotherapy. It is designed to be used in medical and radiation physics courses and by Master and PhD students in medical radiation physics. Designed to be academic as well as practical, it is the first book of its kind suitable for both teaching and researching various radiation dosimetry topics.