Tree rings can be used to determine the age of trees and study environmental conditions in different years. Each year a tree forms a new growth ring, with wider rings indicating better growing conditions and narrower rings indicating drought or other difficulties. By matching ring patterns between trees, scientists have developed tree-ring chronologies that can date back thousands of years. The field of dendrochronology uses these ring patterns to date wood and study past climate patterns, as well as applications in archaeology, geology, and environmental science.