Cancer, a global health crisis, is projected by WHO to cause 10 million deaths by 2020, with a mortality rate of one in six. This has spurred intensive research for innovative treatments. Cancer arises from genetic abnormalities triggering uncontrolled cell division, presenting distinct hallmarks. Both inherited and acquired mutations transform cell behavior, resulting in abnormal growth, reproduction, and death. Environmental toxins and spontaneous mutations contribute to genetic changes, while hereditary factors predispose some individuals. Despite rapid advancements in targeted treatments and immunotherapy, therapy resistance remains a formidable challenge due to the disease's heterogeneity. Understanding cancer biology is crucial for developing effective treatments. This book provides a comprehensive overview, covering basic cell biology, genetics, cancer development mechanisms, immune system involvement, diagnostic methods, treatment modalities, including emerging therapies, and challenges like drug resistance. Geared towards students and researchers in biology, medicine, and oncology, it offers vital insights into combating this complex disease.