Say you are a designer tasked with creating an image. The only specs you have are that the size of the image needs to be one pixel high and two pixels wide. Seems pretty simple, right?
Just considering RGB colors, that gives you 16,777,216 color choices for the leftmost pixel. And another 16,777,216 for the rightmost pixel. Combined, that means that for that 1×2 pixel image, there are over 281 trillion different images you can create. 281,474,976,710,656 to be exact.
If you were to generate every possible image and lay them out in a grid, it would be large enough to fill over 271 million iPhone 6 Plus screens. Or almost 68 million 4K TV screens.
RGB is 16,777,216 colors per pixel. Two pixels means 16 million per pixel, multiply them to get 281,474,976,710,656 different images.
Each image is composed of two pixels, so a grid of all possible images would take up 562,949,953,421,312 pixels.
An iPhone 6 Plus resolutions is 1920×1080, or 2,073,600 pixels. Divide the grid size by that, you get 271,484,352 (and a half) iPhone 6 Plus screens to display all the images.
4K resolution is 3480×2160, or 8,294,400 pixels. So 67,871,088 (and change) 4K screens to display the grid.