Dendrochronology: from the Greek dendron - ou, tree, chronos - ou, time and logos, study. It is a part of Botany that studies rings of annual growth of the trunks of the trees, thus establishing his age and weather conditions during those years. The observation of these growth rings shows a darker area which corresponds to the summer and another corresponding to the spring log clearer; in the tropics to the time of drought and rains respectively. When I was a kid always were admired these rings of the stumps of cut trees that couldn't interpret. What beautiful is nature!