Power bricks are small red 2x2 Lego bricks that can be found in secret areas. They are only available in Lego® Star Wars II: The Original Trilogy and Lego® Star Wars: The Complete Saga. They are also known as red bricks or red power bricks.
There are 18 power bricks in Lego® Star Wars II: The Original Trilogy, 1 per level, with each one unlocking an extra, or cheat, that can be bought at the cantina bar for varying amounts of studs.
There are also 36 power bricks in Lego Star Wars the Complete Saga.