Gigantic Jets (GJ) are lightning discharges between the cloud and the lower ionosphere,
which manifest as leaders at low altitude and transition to streamers as they rise in altitude. The evolution
has never been imaged before at rates faster than 1/60th second. We ran a campaign in northern Colombia
with an intensified high-speed camera at 900 images per second to study the development. The image
sequence reveals a weakly luminous stepwise upward propagation from the cloud top to 40 km altitude,
after which continuous and much brighter branches grow to the ionosphere in 2 ms. We show the stepping
to be consistent with pilot system propagation in streamers.Postprint (author's final draft
