Humans are naturally curious and creative, two traits that have led our species to many scientific and technological breakthroughs. Since our earliest ancestors bashed a rock on the ground to make the first sharp-edged tool, humans have continued to innovate. From the debut of the wheel to the launch of Mars rovers, several of these key advancements stand out as especially revolutionary. Some inventions are thanks to one eureka moment, but most of our most pioneering inventions were the work of several innovative thinkers who made incremental improvements over many years. Here, we explore 20 of the most important inventions of all time, along with the science behind the inventions and how they came about.