About Focus Stacking

Focus stacking is a digital image processing technique which combines multiple images taken at different focus distances to give a resulting image with a greater depth of field (DOF) than any of the individual source images.

https://en.wikipedia.org/wiki/Focus_stacking

In this image you can see my lens sitting on a rail that can move the camera forward or backwards by as little as 2um, or 0.002mm per step.