Crossdating is a method used in dendrochronology (the study of tree rings) to determine the exact age of a tree sample by comparing its ring patterns with those of a master chronology. This technique involves matching the pattern of rings in a given tree sample with the patterns in a larger database of tree ring sequences, which can help researchers establish the age of the tree and gather information about past climate conditions, natural events, and other environmental factors. Crossdating is a crucial tool in reconstructing past climates and environments as well as dating archaeological and historical artifacts.