In the sixth chapter, the Lamb begins to break the seven seals of the book.  The first four seals are accompanied with a rider on a horse.

The first horse was white and the rider (Christ) went forth conquering.

The second horse was red and the rider took peace from the earth.  He was given a great sword.

The third horse was black, and the rider had balances in his hand with which he measures barley, oil and wine.

The fourth horse was "a pale horse" and the one who sat on him was Death.  Power was given to him for the fourth part of the earth to kill with a sword and with hunger, and with death, and with the beasts of the earth.   Mercy.  I hope I am in heaven before this happens.

Then the scene changes as the Lamb opens the fifth seal.  When he breaks the seal, we see a vision under the alter of the souls of all those that were slain for the Word of God, and for the testimony which they held:  There is a book called "Foxes Book of Martyrs" that chronicles those who were killed for their faith.  Starting with Stephen who was stoned to death while Saul (later renamed Paul), held the coats of those who killed Stephen.  Saul had set out to kill all he Christians he could find when God struck him blind on the road to Damascus.  Paul's testimony is one that can not be ignored.  He was a changed man and became the most prolific writer of the New Testament.

The sixth seal brought a great earthquake, and the sun became black, and the moon became as blood. Then the stars fell unto the earth, and the heaven departed as a scroll when it is rolled together.  6:13-14.  All the people of the earth begin to hide from the wrath of God.

6:17 "For the great day of His wrath is come; and who shall be able to stand?"

Then there is a space of time before the seventh seal is broken.