Replisome is a multi-protein complex responsible for DNA replication.The dynamic nature of replisome makes it challenging to detect the transient behavior of the molecular participants in replisome by ensemble-averaging techniques.Single-molecule methods have emerged as powerful tools to study individual replication proteins and their functions within the replisome.The ability to observe the dynamic process that replisome duplicates DNA in real-time provides insight into the molecular mechanisms underlying DNA replication.Single-molecule fluorescence microcopy has led us to an improved understanding of the unwinding mechanism of DNA replicative heclicase, initiation of replication and possible modes of replication termination.