Abstract: A method of diagnosing a disease of a fingernail, a toenail, the skin, or a mucus membrane using a confocal microscope to observe abnormal structures within the fingernail, the toenail, the skin, or the mucus membrane respectively and comparing the characteristics of those structures to corresponding characteristics structures known to be associated with a disease state is taught herein. A method of monitoring the progress of a treatment of a diseases of a fingernail, a toenail, the skin, or a mucus membrane using a confocal microscope to observe changes over time of an infected area is also taught.