Upon reviewing the correlation between the electronic structure and the elastic properties of nanolaminates based on the previously published ab-initio data, the authors suggest that nanolaminates can be described as interleaved layers of high and low electron density. M n+1 AX n phases (space group P6 3 /mmc) can be characterized by stacking of layers of high (MX) and low (A) electron density. Furthermore, the M n+1 AX n phases possess the bulkmodulus-to-C 44 ratio of 1.2-1.7, which in turn gives rise to a combination of ceramic and metallic properties. This design criterion is not only limited to the M n+1 AX n phases, but it can be found in many other phases crystallizing in the same space group (ternary phosphides, Al 3 BC 3 , Zr 2 Al 3 C 5 , and W 2 B 5 based phases) and the related space group P6/mmm (Y n+1 Co 3n+5 B 2n ) as well as in the phases of the cubic Pm3m symmetry (perovskite borides and nitrides).