Two areas of development in the field of glasses and ceramics have produced new materials with unusual combinations of properties. Glass-ceramics are melted and formed as glasses by conventional glass-forming techniques, but by a subsequent heat treatment, they are converted to fine-grained crystalline structures with new and useful combinations of properties. Products with thermal expansion coefficients approaching zero and flexural strengths ranging from 10 000 to 50 000 Lb./in.$^2$ have been made though not all combinations of low thermal expansion coefficients and high mechanical strengths are possible. The second area of development is in so-called Chemcor glasses. Such glass products can be preferentially pre-stressed by chemical means so as to produce an outer layer with high compressive stress and a bending strength in the finished product up to 100 000 Lb/in.$^2$.