Here's a brief video from Lad Allen that presents some amazing facts about the number of stars in our universe, the number of grains of sand in the world and the number of molecules of water in a single drop.
Whether you're inclined to agree with the conclusion of the video or not, the physical facts it presents are not in dispute, and they are mind-blowing.
The video is only five and a half minutes long, but it will surely fill you with a sense of wonder at the size of the universe, both astronomically and microscopically: