T cells, which are lymphocyte immune cells, have largely been used in the past in therapeutic approaches against Leukemia.However, a new type of immune cell called the chimeric antigen receptor-modified natural killer (CAR NK) cell is stealing the spotlight. CAR NK cells are able to fight against many different types of tumors and hematological malignancies. They work in a similar manner to T cells, but they need to be genetically modified to express CARs in NK cells, which will provide them with the ability to target specific tumor types. CAR NK cells have shown to have many advantages when compared to T cells in immunotherapy because they can be engineered to target a wider range of tumors, are quicker to produce, safer since they reduce the risk of graft-versus-host disease (GVHD), and are cheaper.This book discusses various studies on CAR NK cells, the development and potential applications of these cells, and the advantages and disadvantages of a CAR NK cell-mediated immunotherapy.