Formation of the sigmoid in IRIS 1400 Å, AIA 193 and 94 Å, and EM maps at temperature range of 0.5–4 MK. The white and red arrows indicate the sigmoid and the flux rope, respectively. The black arrows show the brightenings. The contours of HMI longitudinal magnetic fields at the closest time are superposed on all panels with positive (negative) fields in blue (green), and the levels for positive (negative) fields are 200 (50), 400 (100), and 600 (150) gauss.