For those like me who witnessed the beginning of the adventure of human mitochon drial pathology, one can only be astounded by the extent and unexpectedness of what the field has come to offer. Extent because nobody could have imagined the sheer size of the domain. Unexpectedness because hitherto it was impossible to imagine the clinical polymorphism that this pathology would represent. The starting point was clear. Initially, there was the exceptional, and for a long time unique, observation of euthyroidian hypermetabolism that Luft and colleagues analyzed remarkably in biochemical and...