The two turning points discussed in this book are exploiting the power of steam, and fabricating clear transparent glass. The first caused the Industrial Revolution that transformed our civilization. Clear transparent glass has not caused an economic upheaval but, as I will argue, has really been a turning point in human civilization.
While the power of steam is associated with water boiling and completing a first order transition into steam, glass is formed by preventing the first order transition of freezing a liquid.
The two turning points discussed in this book were not requiring great technical advances as in nuclear power or in space-technologies. They are both associated with first order phase transitions that are well understood when they occur. But not understood, as in glass formation, when they do not occur! The nature of glass and the glass transition remains one of the unsolved problems of physics.