This is a Chinese legend about the creation of the world. In ancient times, the sky and the earth were combined just like an egg. The founder of the world, Pangu, lived and grew up in the egg. After 18 thousand years, he began to separate the sky and the earth, so the egg white became the sky and the egg yolk became the earth. After another 18 thousand years, the sky and the earth were separated completely. Seeing that his mission was finished, Pangu died of exhaustion. Now people usually use the idiom "开天辟地" (opening up the sky and earth) to describe something advancing with giant strides.