?-Crystallin is the principal lens protein. It is a member of the small heat shock protein family (sHsp) and acts as a molecular chaperone by stabilizing proteins under stress conditions through the formation of a soluble sHsp target protein complex to prevent their aggregation. Macromolecular crowding is ubiquitous in all types of cells and describes the normal conditions inside a cell. The concentration of macromolecules inside a cell is very high (up to 300 mg/mL). Thus, there is a major difference between in vivo and in vitro conditions such as those used in most studies of protein behaviour and properties. In vitro, much work has been published on the interactions of ?-crystallin with target proteins in dilute solutions. In this book in order to better understand the chaperone activity of ?- crystallin under conditions more closely resembling the intracellular environment, its interaction with a range of destabilized proteins in the presence of dextran (68 kDa)have been examined. This book will be very warmly welcomed by scholars of regional science, biochemist, biophysics, proteomics as well as biologist.