Princess Catherine is celebrating another trip around the sun by honoring nature's ability to heal. For her 44th birthday on Friday, the Princess of Wales posted a video titled "Winter," marking the fourth and final installment of her "Mother Nature" series. In it, wearing a green coat and a matching newsboy cap, she strolls over a bridge, takes in the scene while standing in the middle of a field, dips her hand into a stream, and more.