In 1894 Drude became an extraordinarius professor at the University of Leipzig; in the same year he married Emilie Regelsberger, daughter of a Göttingen lawyer.

Drude graduated the year Heinrich Hertz began publishing his findings from his experiments on the electromagnetic theories of James Clerk Maxwell.

He then worked to derive relationships between the optical and electrical constants and the physical structure of substances.

[citation needed] Toward the end of his tenure at Leipzig, Drude was invited to write a textbook on optics, which he accepted.

The book, Lehrbuch der Optik,[2] published in 1900, brought together the formerly distinct subjects of electricity and optics, which was cited by Drude as an “epoch-making advance in natural science.”[3] In 1900 he developed a powerful model to explain the thermal, electrical, and optical properties of matter.