1. An apparatus for viewing a virtual microscope slide data structure containing images of a specimen, the apparatus comprising: a control system configured to retrieve images from the virtual microscope slide data structure and construct a composite image of a portion of the specimen based on at least a portion of the first or second set of images, the data structure comprising a first and second set of contiguous non-overlapping images of the specimen, and coordinating information that relates positions of the first and second set of images, wherein a plurality of images in the first set of images are associated with a first focal plane and a plurality of images in the second set of images are associated with a second focal plane, wherein the second focal plane is displaced relative to the first focal plane.