This unique work presents one of the most significant organ failure condition   cardiocirculatory shock   and the prominent role of Methylene Blue (MB). Through their extensive experience, the authors  consider that the lifesaving feature of MB is still underestimated. For this reason they outline key concepts of MB, mentioning essential experimental data, yet focusing mainly on its application in the care of critically ill patients.  In an easy-to-read format, the 18 chapters were organized in a didactically structured order, distributed in four parts. The first part introduces the general conceptual aspects and physiology of the endothelium. The second part presents the particularities of endothelial dysfunction in different types of shock. Methylene blue is discussed in detail in the third part. In the fourth part, particular situations of endothelial dysfunction, such as heart surgery and organ transplantation, are described.