And in almost any given field, you can go in there and find a particular form of representation which transformed or ignited the field.

The periodic table, for example, Mendeleev's periodic table was basically the beginning of a theory of chemistry. That's where it all started. [more]

Bohr's model of the atom, which of course was originally inspired... See more

Leibniz's notation for the calculus. Leibniz was the UI designer of the 17th century. He was obsessed with notation, always trying out different notations, always talking with his friends about notation. Because he realized that a lot of the power in an idea lies in the form in which it's expressed, because that's what allows people to think it.

Place-value Arabic numerals were the first user interface for numbers that allowed calculation to be done on paper