Exodus begins with laying a foundation for the events that will come to pass. It has been 400 years since Joseph ruled in Egypt and the Israelites are crying out to the Lord for deliverance. God will bring that deliverance about through a baby.
Then Joseph died, and all his brothers and all that generation. But the people of Israel were fruitful and increased greatly; they multiplied and grew exceedingly strong, so that the land was filled with them.Exodus 1:6-7