An accidental discovery led us to correlate a pathology of "unknown origin" with the presence of micro- and nano-particles of inorganic nature in the human tissues. Bioptic samples of livers and kidneys affected by cryptogenic granulomas were observed through a new type of electron scanning microscope called environmental scanning electron microscope and X-ray-microanalyzed with an energy dispersive system. All the randomly selected samples showed the presence of inorganic samples, sometimes varying in chemical composition, but consistent in size (larger in the liver, smaller in the kidney). This article illustrates the results obtained on randomly picked samples and proposes our new investigative method as an aid to achieve a medical diagnosis. Two more items are discussed: the possible, until now unexplained, origin of a pathology as deriving from the presence of exogenous particles, so a new word "nano-pathology" was developed and, as a consequence, the relativity of the concept of biocompatibility as depending on the size of the material considered and its local concentration. The implications of the discovery are briefly discussed.