Cyclin-dependent kinase 1 (CDK1) is a crucial enzyme that plays a key role in regulating the cell cycle, particularly during the transition from G2 phase to M phase. It is activated when it binds to a specific protein called cyclin B, forming a complex that drives the cell's progression into mitosis, where cell division occurs. CDK1 is essential for various cellular processes, including DNA replication and the proper segregation of chromosomes. Its activity is tightly controlled by the presence of cyclins and other regulatory proteins, ensuring that cells divide accurately and maintain genetic stability.