As such chemistry is the study of matter, its properties, and its changes. Read about important terms used to describe matter . This is a very human endeavor, for from the beginning humans have tried to understand by classifying and naming. Clusters and excimers have a very short life-time. No definite composition.
Definitions depend upon scale.
A homogeneous mixture may be heterogeneous if you look closely enough. The solute vs the solvent. The history of chemistry is as long as human history. Progress is measured by advances in chemistry. Recent progress in science including chemistry is a consequence of the use of the scientific method .