Pascal's Law states that pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and the walls of the containing vessel. In a hydraulic brake system, a small force applied to the brake pedal creates pressure in the master cylinder. This pressure is transmitted equally through the brake fluid to the slave cylinders at the wheels. The slave cylinders have a larger area than the master cylinder piston, resulting in a much larger force being applied to the brake pads or shoes, pressing them against the discs or drums to slow down the vehicle.