A thousand times in history a baby has become a king, but only once in history has a king become a baby. (Often quoted but source unknown)
The Incarnation is fundamental to the Christian faith. Manger scenes often give people tender thoughts about the Christ child, meek and lowly. The Bible teaches that the baby Jesus was God Himself, taking on human flesh to demonstrate what godly living is and to provide a way for men and women to become a part of the kingdom over which He will ultimately reign.
For God is the King of all the earth. (Psalm 47:7)