I agree. The important advance in the first half of the 20th century was understanding how atoms work, and that knowledge lead <i></i>directly<i></i> to semiconductors, the nuclear industry, and laid the foundation for modern chemistry, materials science and all the analytical technologies than enable chemistry, physics etc (i.e. x-ray analytical techniques, mass spectrometers).<p>Something that I did not know until recently was that the &quot;mineralogy&quot; of steel was not understood until the 20th century. If you do not understand the phases comprising a material, it is difficult to relate bulk material properties to bulk composition.