It has been experimentally verified that melatonin has various biological functions of much interest, but the today's trend harboring an idea that melatonin is likely to be a cure-all is extreme by any stretch of the imagination. What should be now sought will be to take a short rest from experiments and to arrange a huge number of experimental data so far obtained as well as to judge calmly the real state of things. I have had a very happy experience in extending melatonin study from so-called classic to modern parts of it. But the problem of it, which all the time had something been on my mind was that no theoretical linkage was likely to be gained between a classic part of the experiment, that is, more lightening of amphibian skin colors and a modern part, that is, its influence on mammalian lipids or immune systems. An idea occurred to me, as far as my research results are concerned, that the major part of such a linkage between both can be put in order by understanding that the feature of melatonin is a direct or an indirect functions of the anti-ACTH . glucocorticoid system. And probably, this way of thinking helps arrange many other results of melatonin research.