The phenomenon of electric discharge and light emission within the cloud, between clouds, and between cloud and ground. Due to strong convection in a cumulonimbus, the water droplets or ice crystals generate static electricity while friction between particles. If these charged particles are strong enough, they will discharge which is the so-called lightning. If lightning only occurs in the clouds or extends in the sky, it is called inter-cloud lightning; if the lightning is released to the ground and hits an object on the ground, it is called ground lightning. Lightning is the most violent and dangerous phenomena in the atmosphere. When lightning occurs, you must enter the room to avoid lightning strikes.