Scottish biologist, mathematician and scholar D'Arcy Wentworth Thompson (author of On Growth and Form) as quoted by his daughter in Ruth D'Arcy Thompson, D'Arcy Wentworth Thompson, The Scholar-Naturalist. London: Oxford University Press, 1958, p. 175—
You choose some subject or other which takes your fancy, you buy a notebook and label it with the title of your theme; and you keep jotting down therein whatsoever bears upon your subject, as it comes your way, in all your reading, observation and reflection. I have had many such notebooks and some I have soon grown tired of but others have lasted and served me well… Your subject opens up wonderfully as time goes on, it tempts you into byways, it carries you far afield; if you play the game aright it never comes to an end. It grows in interest continually, for things are interesting only in so far as they relate themselves to other things; only then can you put two and two together, and see them make four or even five, and hear them tell stories about each other. Such is science itself and such is all the knowledge that interests mankind.