Tree trembling, also known as ASPEN, is a phenomenon in which trees shake or tremble due to strong winds or other external forces. It is most commonly seen in ASPEN trees, hence the name, but can occur in other species of trees as well. The shaking of the tree is caused by the wind blowing against the leaves and branches, causing them to vibrate and create a trembling effect. Tree trembling can be both beautiful and dangerous, as it can cause damage to the tree and surrounding structures.