There are giants. There are millions upon millions of giants. They live all around the world, they're everywhere.
The giants are dangerous. They hate everything, especially us, but even each other. They kill indiscriminately. It's possible to kill the giants, though, despite their immense size. In fact, a great many of them have been killed, even by creatures as small as us.
The endless war, which has existed ever since they first came to this planet and tried to take over, goes on and on. Many on both sides don't even notice the war, since it's so scattered and hard to predict... but the war still goes on and billions upon billions of us die. The giants can kill billions of us, but they'll still lose the war, eventually. It's just a matter of time, of waiting them out. We were here first, and we'll still be here after they're long gone.
The bigger they are, the harder they fall.