1. Introduction

Colloids owe their name to Thomas Graham (1805-1869), a British chemist who used this term to describe a liquid state of matter that diffused with difficulty through semi-permeable membranes, unlike crystalloids (consisting, for example, of a saline solution), which diffused rapidly. The word colloids was coined from the Greek (kolla: glue, gum, eidos: appearance). Graham understood that this was a new state of matter corresponding to a heterogeneous structure and, in fact, dispersions with a characteristic size between 10 ^–9 m (1 nanometer) and 10 ^–6 m (1 micrometer). In the article that gave colloids...