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This chapter discusses various approaches that explain the glass transition phenomenon. Understanding of glass transition phenomenon contains primal importance in the study of glasses. The glasses are disordered solids and hence it should be subjected to view glass transition as a feature of the amorphous solid state. The first major development in this direction is the formulation of the free-volume theory of liquid viscosities. This is the approach made in the bond-lattice model. Bond-lattice model is relevant in several other contexts as well. The cluster model of glass transition gives primacy to the presence of heterogeneity in glass structure. Glass transition occurs when a major part of the melt is transformed to clusters and the remaining material simply freezes into a tissue of lower density as compared to clusters.

This chapter explores the physico-chemical principles of inorganic glasses. The glass industry has witnessed significant developments over the past several years. The 20th century witnessed the emergence of glass as an integral part of human life as well as the evolution of manufacturing techniques and a deeper scientific understanding of glasses. Growth of glass science is connected with the growth of chemistry and physics, particularly of inorganic materials. The high degree of chemical inertness of the surface of silicate glasses and the workability of glass into large and desired shapes of any complexity made them a natural choice for use in chemical laboratories. Following the industrial revolution, glass making became the business of factories. Thick sheets of flat glass—plate glass—are made by a special float process where melts are made to settle and freeze on molten tin pools that provide optically smooth and parallel surfaces. Glasses are colored with added oxides or halides and made to change their colors or become darker on exposure to light or heat.

There are frequent allusions in Shakespeare's plays to physical and mental characteristics and qualities of individuals that often reflect genetic and related insights, ideas and implications with a bearing on the determination of these phenotypes. Quotations from the plays with comments are presented here to indicate varied perceptions in these regards that Shakespeare brilliantly conveyed some 400 years ago through many of his 'dramatis personae'.

In the second part of his article about Shakespeare's references to the medical profession, the author selects quotes that show some positive and negative images of the doctors of the day.