John was to write down what he sees but the book contains letters written to the saints in seven cities (ekklesias) in chapters two and three and opens with a grand vision of the present position and power of Jesus Christ. Therefore, one could see the book structured in the following way.
Threefold Structure Based on 1:19  “Write therefore the things which thou saw, and the things which are, and the    I. What You Have Seen (1:1–20)      things which shall come to pass hereafter.”
II. What Is Now (2:1–3:21)
III. What Will Take Place Later (4:1–22:21)
Others see a chiastic structure that is common among writers.
Chiastic Structure
A Prologue and Greeting (1:1–8)
B Seven Cities of the Called-out (1:4–4:2)
C Seven Seals (3:21–8:5)
D Seven Trumpets–Angels–Two Witnesses (8:2–11:19)
E Woman, Dragon, and Male Child (12:1–17)
D Two Beasts–Angels–Seven Bowls (13:1–16:21)
C ‘ Destruction of Babylon (16:18–19:10)
B’ New Jerusalem, the Bride (19:6–22:9)
A’ Closing and Epilogue (22:6–21)
Sevenfold Drama Structure
Prologue (1:1–8)
Act 1 The Seven Golden Lamp Stands (1:9–3:22)
Act 2 The Seven Seals (4:1–8:4)
Act 3 The Seven Trumpets (8:5–11:18)
Act 4 The Seven Visions (11:19–15:4)
Act 5 The Seven Bowls of Wrath (15:5–16:21)
Act 6 The Seven Judgments (17:1–20:3)
Act 7 The Seven Great Promises (20:4–22:5)