1. A method of accessing a site on a biological substrate, comprising: utilizing a first fiducial level system to determine at least one of a position of a first area and an orientation of the first area of said substrate relative to a first datum point; utilizing a second fiducial level system to determine at least one of a position of a second area and an orientation of the second area relative to said first datum point, wherein said second area is smaller than said first area; accessing at least a portion of said second area with an access device.