Calculus - the mathematical study of continuous change - was a revolution in mathematical thinking.
Calculus studies the computation of limits, derivatives, and integrals of functions of real numbers, and in particular studies instantaneous rates of change.
Gottfried Wilhelm Leibniz and Isaac Newton developed Infinitesimal calculus independently in the late 17th century. It was refined by Cauchy,Weierstrass, and Riemann. Calculus is used in science, engineering, & economics.
It is the gateway to most STEM careers.