It began when God saw all the human beings full with sin. God had an idea and get rid of all the humans and animals on this planet. But before he did the crisis, he told his favorable human Noah, to bring his family and 2 of every animal on a boat so that they can live the crisis and make sure to repopulate.
The first thing that happened is that God saw grieve in his heart because all Humans have some Sin in them.
Next, God decided to flood all of his creations and erase all of Humans and with the animals.
Finally, before God did the flood, he told his favorable Human Noah, to bring his family and animals so that they can repopulate after the Crisis was over.
A life lesson we can learn from this passage is that if we are to not sin, we will be rewarded, just like how Noah had no sins and he was able to live the Crisis with his family and every animal to repopulate.