“…One such prime example would be 3d–4f mixed-metal complexes. − Notwithstanding the initial skepticism, the concomitant presence of transition metals and lanthanides for the construction of a polynuclear cage and clusters has proven to be highly rewarding, with markedly improved magnetic, chemical, optical, and other physical properties. − Of particular interest is the deliberate mixing of f and d electrons to induce stronger interactions vis-a-vis individual d–d or f–f electrons to transcend the magnetic, electronic, and optical properties, and their mutual interplay is now well documented. , Subsequently, the last few decades have witnessed a phenomenal upsurge of interest in studies of mixed-metal complexes. , Almost every possible combination of 3d–4f complexes has been explored. − The emphasis of initial works is more or less “one-dimensional”; that is, they aim to optimize one particular property like magnetism or optics. − With advancement of the subject, however, other potential uses of these complexes soon become increasingly apparent . Moreover, instead of using randomly chosen pairs, a specific combination of 3d and 4f metals with the aim of culminating their characteristic properties starts to dominate the design strategy, aiming to kill two birds with one stone .…”