NOAA Lightning Animation (IMAGE) University of Utah Caption The bright flash of light is only one stage of lightning; there's a substructure that happens too fast for the eye to see. 'Step leaders' proceed toward the ground in stages. Negative electric charge builds at the leader tip until it is sufficient to cause the air to break down and form a new conducting path. The study found that terrestrial gamma rays are produced within the first 1-2 milliseconds of the initial breakdown stage, which is the least understood part of lightning. Credit National Oceanography and Atmospheric Administration Usage Restrictions non commercial with attribution License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.