The custom of having a decorated Christmas tree dates back to the 15th century in Germany. The tree was originally a symbol of fertility and was decorated with fruit, nuts, and other foods. It wasn't until the 18th century that the tradition of putting lights on the tree became popular, and it was around this time that the Christmas tree became a staple of the holiday season. Over time, different cultures have added their own unique touches to the tradition, such as ornaments and tinsel, creating a truly diverse and beautiful representation of the holiday spirit.