A molecular clock is a scientific method used to estimate the time of evolutionary events by analyzing genetic mutations. It operates on the principle that DNA and protein sequences accumulate changes at a relatively constant rate over time. By comparing these sequences among different species, researchers can infer when they diverged from a common ancestor. This technique is particularly useful in the study of evolution, as it helps to construct phylogenetic trees that illustrate the relationships between species. The molecular clock can also be applied to understand the timing of events such as speciation and the emergence of diseases.