Discovery of Boyle's Law: He studied the compression of gases. Doing his experiments, he observed that "At a fixed temperature, the volume of a gas is inversely proportional to the pressure exerted by the gas."
Real world example: The popping of a balloon is a real world example. When we try to squeeze the balloon, we are trying to reduce the volume of what is inside, which increases the pressure. Because of the excess pressure, the balloon bursts.