So much photography today is a composite of multiple images, 3D assets, and painted components blended together with Photoshop. It always blows me away when I see a video like the one below that shows what goes into making a composite image.
The video is a behind the scenes look at Kristina Varaksina photoshoot for the image Space Awaits. It shows all the stages from her initial digital sketch to shooting, to editing, retouching and using a 3D model, to the final post production.
The video itself is short, just two and a half minutes long and not deep on detail, but it does give a solid insight into the process behind the finished shot.