Congress's Response to Presidential Veto

The system of checks and balances in the United States is defined by the interplay between the executive, legislative, and judicial branches of government. Each branch has specific powers that are designed to limit the actions of the other branches, thereby preventing any one branch from overpowering another. An example of this system in action can be seen when a president vetoes legislation passed by Congress. In this scenario, what is the mechanism that Congress has to counter this veto?