Concerning water, the most apparent feature is that the behaviour in k-space looks just the opposite of that in r-space seen in Fig. . Namely that there is more dispersion for the alcohols between the various atom-atom correlations, while that of water are superposed. In other words, in k-space, it is water which looks more homogeneous than alcohol, the exact opposite of what we found in r-space. Seen from a k-space perspective, water appears as more isotropic and homogeneous. We believe that it is precisely at the origin of the contradicting dual pictures of water, both as a structured liquid and as an ordinary liquid of small molecules . The rst picture could account for the rich microscopic dynamics of water in the real space, while the second picture could refer to the almost disappointingly simple dynamics of all atom-atoms decays in k-space. The present analysis provides both a microscopic support for the two interpretations and an explanation for the apparent contradiction. In view of the related controversies in the past, the present analysis provides a resolution of an old problem.