Anatomy of a Tree Ring A tree during the winter months stands dormant, but during the spring (or during the wet season, in some areas), it begins to grow. It actually experiences a growth spurt -- with new cells growing between the previous year's tree ring and the tree's bark. The cells that grow during this initial period are large. As the season progresses, however, the cells that form are smaller and smaller. These smaller cells appear darker. The difference in appearance between the smaller latewood cells and the following season's earlywood cells creates a striking delineation. The ring represents one year in the life of the tree. Anatomy of a Tree Ring Next: Growth and Sensitivity Skeleton Plots Photo credits Printer-Friendly Format   Feedback Explore the Methuselah Grove | A Tree's Secret to Living Long Build a Tree-Ring Timeline | Illuminating Photosynthesis Resources | Teacher's Guide | Transcript | Site Map | Methuselah Tree Home Search | Site Map | Previously Featured | Schedule | Feedback | Teachers | Shop Join Us/E-Mail | About NOVA | Editor's Picks | Watch NOVAs online | To print PBS Online | NOVA Online | WGBH © | Updated November 2001