Isaac Newton (1642–1727) had a rather tough childhood. His father died during his mother's pregnancy and his mother remarried when he was three years old—and left little Isaac in the care of his grandmother.

In 1661, Newton entered Trinity College in Cambridge, and graduated with a BA in 1664, after an unimpressive student career. But then the university shut down for two years because of the Great Plague, and Newton, back in his native Woolsthorpe, laid the ground for much of his future work in the anni mirabiles 1664–1666. He invented calculus (his method of fluxions) and the law of gravitation, and showed by experiment the prismatic composition of white light. All this before he turned 25. (Inventing calculus means that he developed a widely applicable theory; its roots go back, of course, to the work of many people, Archimedes and Fermat among them.)

Back at Cambridge, Newton became Lucasian Professor of Mathematics, at the age of 26. His former teacher, Isaac Barrow, resigned from that position to make way for the greater scientist (and to prepare his own move into a better position as chaplain to King Charles II). At that time, Newton was the prototype of the “forgetful professor”, rather negligent about trifles such as his appearance. His nephew Humphrey Newton wrote: He very rarely went to Dine in ye Hall unless upon some Publick Dayes, & then, if He has not been minded, would go very carelesly, wth Shooes down at Heels, Stockins unty'd, surplice on, & his Head scarcely comb'd.