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.

3D Transmitted LightStereo-pair photomicrograph taken with reflected incident light to show the interlocking pattern of a feather. Mag. 50x. (Photomicrography by Dr. Gary L. Greenberg)

Head region of chick embryo, showing closure of the neural tube (L-R view). Advantages of Multiple Oblique™ illumination include the ability to visualize living, thick, unstained, tissue by introducing contrast without sacrificing resolution. LWD 20x objective. (Photomicrography by Dr. Gary L. Greenberg)