Microclusters are tiny aggregates of matter consisting of two to several hundred atoms, and as such constitute a new distinct phase of matter. Microclusters are the intervening state of matter lying being monoatomic elements and matter consisting of sufficient numbers of atoms so as to constitute the states of matter we normally associate with various elements and compounds.
For example, metals in the normal state of matter exhibit electrical conductivity via the sharing of free electrons. However, as smaller and smaller samples of a metal are accumulated -- to the extreme of becoming a microcluster of the metal -- the characteristics of the solid metal begin to change and in some cases disappear altogether. This could include changes in the phenomena of conductivity.
The concept of Microclusters as a transitional phase between solids and monoatomic elements or compounds is of potentially enormous importance. And just as in the case of water, one might suspect that the direction of the phase change, whether from microcluster to solid or vice versa, may be of particular importance as well. As researchers and chemists, Michael Duncan and Dennis Rouvray have addressed what might be considered the traditional version of this concept: "Divide and subdivide a solid and the traits of its solidity fade away one by one, like the features of the Cheshire cat, to be replaced by characteristics that are not those of liquids or gases. They belong instead to a new phase of matter, the microcluster."