Videos of 3D development of simulated negative stepped leader with a feeding currents of 100, 200, and 300 A. 2D projections of discharge channels on the x-y, x-z, and y-z planes are shown on the right. Leader channel sections (with conductivities larger than or equal to 1 S/m), including the primary negative leader and space leaders, are shown in various shades of red with darker color corresponding to higher channel conductivity. Channels of the negative leader streamer zone (negative corona streamer burst) are shown in light orange. Positive and negative space streamer channels are shown in green and grey, respectively. Black dots denote space stems, and blue and pink dots denote negative and positive space charges forming the leader channel corona sheath, respectively.