This book, part of the European Society of Intensive Care Medicine (ESICM) textbook series, is a graphical, dense and concise text describing fundamental theoretical concepts needed for doctors and other professionals new to the field of Intensive Care Medicine. The book serves two main purposes: as study material for any junior doctor, nurse or other allied healthcare professional who is time-pressured and wants to quickly learn the essentials; and as a course volume of new ESICM educational initiative called Intensive Care Fundamentals©. The overarching goal of this initiative is to offer standardised high-quality introductory education to all starters in intensive care.  There are two key elements of this initiative: the book, which is the prerequisite reading for attending the two day face-to-face course and the materials, registration of candidate and training and certifying the trainers that will be provided by ESICM.