A virtual microscope slide includes images of a specimen for a given level of optical magnification which are associated and stored in a data structure. The forming of the data structure having the multiple Z-plane images preferably includes automatically focusing at a principal reference focal plane and capturing and digitizing an optically magnified reference Z-image and then shifting the specimen relative to the lens system by a predetermined increment to capture and digitize another Z-plane image. Preferably, a multiple sequence of Z-plane images above and below the reference image and captured and digitized. For ease of retrieval and use, each reference image has its associated Z-plane images are formed in a stack that is sent over the Internet, or Intranet to a local computer storage for quick retrieval when a viewer wants to mimic a focusing up or down to better view a detail in an image. Thus, the resultant images are retrieved and displayed such that a virtual focusing capability is available to the user. The images can be formed with overlapping fields of depth, adjacent fields of depth, or wholly separated fields of depth.