This review by Douglas Hanahan synthesizes the Hallmarks of Cancer, a conceptual framework used to organize the immense complexity of the disease into logical principles. It defines cancer through four distinct dimensions: acquired functional capabilities, enabling phenotypic characteristics, specialized cells within the tumor microenvironment, and broader systemic interactions. The text details nine hallmark capabilities, such as sustaining growth signals and evading immune destruction, alongside enabling traits like genomic instability and chronic inflammation. Hanahan also emphasizes the role of non-cancerous accessory cells and physiological factors like aging and obesity in driving tumor progression. Ultimately, the source proposes that co-targeting multiple hallmarks with combination therapies could overcome drug resistance and improve patient outcomes.