Haemostasis involves a set of strictly regulated processes that maintain blood in its fluid state within the vascular bed and, in case of vessel injury, promote the formation of platelet plugs and fibrin clots to prevent blood extravasation. As such, this book explores how platelets play an important role in the blood coagulation process, and how platelet deficiencies or functional defects may be the cause of some bleeding disorders. The worldwide incidence of cutaneous melanoma has been increasing annually at a more rapid rate in comparison to any other type of cancer affecting predominantly young and middle-aged individuals. It is known that when melanoma cells leave the primary tumour and enter the blood stream, they activate surrounding platelets via some molecules, inducing microthrombus formation. The authors discuss how platelets contribute to inflammation, cancer invasion, and metastasis. Additionally, the role of platelet-rich-plasma in stimulating the healing process in difficult-to-heal ulcers has been investigated over the past 25 years. It is suggested that platelet-rich-plasma is capable of transforming the difficult-to-heal skin ulcer with low metabolic activity into a healing ulcer with increased capacity for tissue regeneration. This closing study focuses on the causes, diagnosis, and prognosis of various types of thrombocytopenia, providing an outline on the future prospects of using antioxidants for the treatment of a few thrombocytopenic conditions.