The tradition of decorating a tree with ornaments and lights at Christmas can be traced back to medieval Europe, where the Christmas tree was first introduced by the Germans in the 16th century. They would decorate evergreen trees in their homes with candles and small ornaments to symbolize the light of the world that came with the birth of Jesus. Over time, this tradition spread to other parts of Europe, and eventually to the United States, where the Christmas tree became a beloved symbol of the holiday season.