Introduction

Abstract

From the time of John Dalton, when the atomic theory became generally accepted, the study of how matter behaves has divided into two streams. One has been reductionist, concentrating on the properties of individual atoms and molecules. In the 1930’s, this line led to nuclear physics and then to particle physics. The other stream has emphasized the properties of very, very many atoms or molecules together, so many that the aggregates they make can be treated as infinite. The realm between these limits concerned only a few independent souls until about the late 1970’s. Since then, interest has grown almost explosively in the study of what have come to be called clusters.