Tree rings are the concentric circles found in the cross-section of a tree trunk. Each ring represents one year of growth, with the width of the ring indicating the growth rate for that year. Factors such as climate, soil quality, and water availability can influence how wide or narrow a ring becomes. Scientists study tree rings through a process called dendrochronology. This technique helps researchers understand past environmental conditions and can even date historical events. By examining the patterns in tree rings, scientists can gain insights into climate change and the health of ecosystems over time.