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The cover picture shows the blue northern French sky and the central [Co(H2O)(NC)5]2– unit of the fascinating Prussian Blue analogue. This material undergoes spin-transition and electron transfer from an FeII to a CoIII site, upon external stimulation, i.e. visible light. Overall, it passes from a diamagnetic to a ferrimagnetic state. The intrinsic {Fe(CN)6}4– vacancy leads to a replacement of an apical cyano ligand by an aqua ligand. Like a hammer hits a nail, this vacancy seems to provoke a deformation of the CoIII ion out of the equatorial plane. Our quantum chemical investigation attributes thus an important role to the apical vacancy. Details are discussed in the article by T. Krah, N. Ben Amor et al. on p. 5777 ff.