Who is the greatest in the kingdom of heaven?

Matthew 18:1–3 (KJV 1900)
At the same time came the disciples unto Jesus, saying, Who is the greatest in the kingdom of heaven? 2 And Jesus called a little child unto him, and set him in the midst of them, 3 And said, Verily I say unto you, Except ye be converted, and become as little children, ye shall not enter into the kingdom of heaven.