Eikon means image, likeness, or representation. It can refer to (1) a portrait or engraved image (Caesar's image on a coin — Matthew 22:20), (2) humans as the image of God (1 Corinthians 11:7; Colossians 3:10), (3) the image of the beast (Revelation), and most profoundly (4) Christ as the eikon of the invisible God (Colossians 1:15; 2 Corinthians 4:4).
Eikon theology is among the richest in the New Testament. Colossians 1:15 — 'He is the image of the invisible God' — means Christ is not merely like God but is the exact, personal representation of God's invisible nature. This is the climax of Genesis 1:26-27, where humanity was made in God's image (LXX: eikon). Christ is the perfect human and the perfect image — what Adam failed to be, Jesus fulfills. Believers are being transformed 'into his image' (2 Corinthians 3:18) — the eschatological restoration of the imago Dei through the Spirit. Creation, fall, redemption, and glorification are all structured around eikon.