This collection of photos is really neat, and spans from biology to physics and space exploration to the very first photograph ever taken. I won't spoil them for you, but you should really check them out for yourself!
www.popularmechanics.com/science/space/nasa/10-scientific-images-that-changed-how-we-looked-at-the-world
www.popularmechanics.com/science/space/nasa/10-scientific-images-that-changed-how-we-looked-at-the-world