The Oklahoma Lightning Mapping Array can map up to twelve thousand points per second, and so can reveal where a flash originates and how it develops in a storm. An example of a flash is shown in this figure. The top two panels show altitude as a function of time. The second of these is a more expanded view, from 20:00.6 – 20:02.2 UT (a period of 1 minute 36 seconds). Color coding indicates elapsed time, with purple being earliest and red being latest. The bottom left panel shows the view one would have from above the storm. The panel just above it shows the view from the south. The lower-right panel shows the view, rotated on its side, one would see from the west. The tics in these three panels are labeled in kilometers from the center of the lightning mapping array, so the east and north dimensions are each 120 km. This flash is longer-lasting and somewhat larger than “typical” lightning flashes. It spans roughly 80 km (50 miles) in the east-west direction. Note how the flash structure extends outward from the dark blue region in which the flash began. This case also shows the classic bi-level structure of flashes. In this case, as in the majority of flashes, lightning channels in the upper layer (well, ok, the layer tilts downward to the west) propagate through positive charge, and channels in the lower layer propagate through negative charge. This bi-level lightning structure results because most storms tend to have a large region of positive charge above a large region of negative charge.