Passing kidney stones is supposedly one of the most painful experiences a person can go through, and these images of one under a scanning electron microscope show us what they look like up close.

The images are from a lab at Eastfield College in Dallas. Its coordinator, Murry Gans, took the photos in 2012 after a colleague brought him a kidney stone to examine, like all colleagues would.

Kidney stones develop when your urine can't dilute all of the substances in it, like calcium and uric acid. Those substances stick together and form these terrifying, spiky crystals. If a stone pushes itself out of the kidney and into the ducts that take urine to the bladder, it can cause a significant amount of pain until its passed out of the body through urination.

There isn't any one cause for that buildup. Some metabolic disorders, genetic conditions, and dietary choices might contribute to their development. The stones' size varies too, from a stone so small it doesn't hurt to pass to ones that need to be broken up with a shockwave treatment.

More photos of the stones can be seen on Gans' blog.