Modern Physics is an origin story of extremes. Extreme speed. Extreme smallness. It was in these corners of reality that old notions found their limits and new ideas could rise to solve mysteries.
A hot cup of coffee and a cold cup of ice water, observed over hours, teach us about some of the things heat energy does, and in response to that, what temperature does. But what IS temperature? Figuring that out leads us down one of the many roads to the quantum universe.