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.

     

Surface of pollen grain.
Taken with 100x objective. (Photomicrography by Dr. Gary L. Greenberg)

     

Stereo pairs of the fern, Ceratopteris.
The green cells are from the gametophyte. (Dr. Stephen M. Wolniak, Department of Botany, University of Maryland.)