The regulation of the cell cycle is essential for ensuring proper cell division, growth, and function. The cell cycle comprises a series of stages through which a cell progresses, ultimately leading to division. Regulation is crucial for maintaining genomic integrity and preventing abnormal cell division, which can lead to diseases like cancer. The key aspects of cell cycle regulation include checkpoints, cyclins, cyclin-dependent kinases (CDKs), tumor suppressors, and oncogenes. The cell cycle is divided into distinct phases: G1, S, G2, and M. G1 is the phase where the cell grows and prepares for DNA replication, S phase is where DNA replication occurs, G2 involves preparation for mitosis, and M is the phase where cell division takes place. The progression through these phases is tightly controlled by a complex network of regulatory molecules. One of the central elements in cell cycle regulation is the cyclin-CDK complex. Cyclins are regulatory proteins that accumulate and degrade at specific stages of the cell cycle, while cyclin-dependent kinases are enzymes that, when activated by binding to cyclins, drive the cell through different phases of the cycle. The activation of CDKs is crucial for the transition from one