Countless years ago there was nothing. Until The Celestials emerged from nothingness and they created the universe we know from nothingness. Every star, every tree and every living being... everyone owes their very existence to them. As they shaped the universe billions of years passed. The galaxy grew larger and larger, larger and larger until they realized the current population cannot control it any further. So they started The Circle. Basically what The Circle meant was: when the galaxy grew too large in a direction, they planted a seed of a Celestial in a planet. As life blossomed on the planet, the Celestial inside was feeding itself with the life force of the planet, getting ready to emerge.
The earth was no different...
Carol was a lone wolf along the endless galaxy. Every problem she encountered, she tried her very best to punch through the solution. Sometimes it worked, sometimes it didn't but she prevailed to this point in her life either way. These few months behind her was a bit different though, she had a partner to assist her against the terrorists who kidnap children from outer galaxy to the center and sell them as slaves... or even worse. Spread all around the galaxy, clearing their filth was no easy task. Sleepless nights, blood and pain were 3 subjects that could describe her 5 months away from earth.
She and her colleague who turned out to be a good friend of her flew back to earth. Carol was eager to see her home, her friend and the episodes she missed in 5 months. She was telling how excited she was to see her home again while looking at her friend's face until her friend pointed at the earth for carol to look. They saw a some kind of red giant and the earth shattering in the middle. The pure energy that released from a newborn Celestial pulled Carol and her friend in. With more energy flowing through inside them, their skin shattered and eventually fainted for a day.