Answer :
e.g.: President-Congress: the President (executive branch) is the commander in chief so in theory he has full control over the military. However the Congress (legislative branch) enacts the budget and grants the President funds for the army. This way the Congress can limit the President by cutting his funds. This goes to all agencies that the President controll. The Congress also approves most of the Presidential nominations, but the President may veto their legislation. The Congress may pass over the Presidents veto, but it would be the agencies controlled by the President thath would implement and execute the laws enacted by Congress. This way every party has some means to obstruct the other and so cooperation and compromise is the only way for the government to operate.