The narrator begins Book 7, imploring his Muse, Urania, to descend from Heaven. She's not one of the traditional nine muses of Ancient Greece; she predates those pagan figures.
She helped him aspire to (i.e., sing about) Heaven, and now he wants her to help return to earth. For the rest of the poem, he will sing "Standing on earth."
It's safer there, even though he (John Milton) is surrounded by dangers. He asks his muse to protect him from the fate that befell Orpheus (the "Thracian bard"), who was torn to pieces.
Adam and Eve have listened attentively to Raphael, and now Adam wants to know more, especially about the creation of the world. He asks Raphael to say why and how God created the world.
Raphael says he'll tell him, though it too will be tough to explain. He warns Adam not to get too curious after he leaves; knowledge is like food, he tells him, and also must be rationed, otherwise one will get sick.
God, Raphael says, sees Satan fall and tells His Son that he will now create another world, lest Satan boast that he took a bunch of angels with him.
According to God, there will be one man that will give birth to an entire race; but he'll live somewhere else, not in Heaven.
God tells his Son that he'll give His Son the power to create another world (he's sub-contracting the job to His Son).
There's much rejoicing in Heaven as the Son comes forth; the gates of Heaven are opened, and he (here called the "Word") bids the "troubled waves" of the abyss to be still as he rides into Chaos.
A bunch of angels follow him to watch the creation; he takes a golden compass and measures out the bounds of the universe.
He infuses "vital virtue" and "vital warmth" into the abyss while also moving the black, lifeless matter far away. He then groups ("conglobe") like substances into spheres, such as the earth.
Then comes the famous "Let there be light," as God divides night and day; the angels praise his creation as the first day comes to a close.
On the second day he creates the "firmament," which is something like the atmosphere that acts as a buffer between the waters on the surface of the earth and the heavens.
On the third day he creates dry land; mountains emerge as various forms of water (streams, etc.) make their way to the sea.
God names the huge bodies of water "seas" and orders that grass, trees, and vegetation come forth. The formerly barren earth all of a sudden blooms as the third day ends.
On the fourth day he creates the sun, moon, and stars to make the divisions between night, day, and the seasons clear.
On the fifth day, he creates reptiles, birds, and whales; he says to them "Be fruitful, multiply." Many other animals breed and populate the oceans, creeks, etc.
On the sixth day, He creates the "beasts" of the earth, such as cattle, lions, tigers, and others. He also makes insects (such as bees), worms, and other little creatures. But there's still something missing.
God says to His Son, "Let us make now Man in our image," which he does. He also creates a female, Eve, to be his companion and says to both: "Be fruitful, multiply, and fill the earth."
He places them in Eden, gives them dominion over everything, and says they can do anything except eat from the Tree of Knowledge.
The Son goes back to Heaven amidst rejoicing; he returns to sit as His Father's side and rest from his six-day labor. The seventh day is now hallowed, though not in silence: music, harps, and rejoicing are heard throughout Heaven.
Raphael finishes, and asks Adam if there's anything else (within reason) that he would like to know.