Relax your eyes until you see a fourth image appear. Depending on whether  you  cross or separate your eyes, one of the two images in the middle will be the correct 3D image and the other middle image will be the opposite direction 3D.

Turnip yellow mosaic virus crystal The 3D perspective provides a clear understanding of the crystal structure that cannot be obtained from a single, 2D photo. LWD 10x. (Dr. Yuri Kuzentsov, UC Riverside, CA.)