Colossians is the seventh of Paul's Epistles. It was written around 61 AD, whilst Paul was imprisoned in Rome, to the Church in Colosse which is in modern day Turkey. Paul had never visited this church, but he knew its founder; a man named Epaphras. Paul had converted Epaphras when he spent three years in Ephesus. Epaphras went to Rome to see Paul and to raise his concerns about false ideas which are being taught in Colosse. On hearing the news Paul wrote this letter to the Colossians, warning them that what they were teaching was lessening the value of Christ. His letter gave them proper understanding of who Jesus was and what He did.
Colossians 1:26-27
"even the mystery which hath been hid from ages and from generations, but now is made manifest to his saints: to whom God would make known what is the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory"