This book covers the essentials of a few types of blood cells and goes on to discuss the number of these cells both under healthy conditions and during disease (can we say in sickness and health?). Results from research papers have been shared to enable a reader to see that the data is backed by actual findings. An important aspect is then covered-blood transfusion. This becomes very important in today's scenario given the pandemic. In fact, the Red Cross issued a statement of dire shortage during the pandemic, which seems to have spilled over after the pandemic. Many of these chapters have included the relevance of artificial intelligence (AI) given the booming interest and emergence of this field.