映雪囊萤

In the Jin Dynasty, there was a man named Che Yin who was fond of learning but because of his family's destitute（赤贫的，缺乏的） conditions, his father could not afford to offer ideal conditions for studying. In order for them to have enough to survive, they could not even buy lamp oil for him to study at night, so he could only recite his poems in the daytime.

On one summer night, when he was practicing reading an article, he suddenly saw many fireflies lighting up the sky. They were a spot of brightness in the stark blackness of the sky. He had a thought: If many fireflies could be contained all together, they might be able to serve as a lamp. Upon having this thought, he found a white silk bag, caught as many fireflies as he could, and hung up this bag. Although it was not as bright as a lamp, it worked well enough that he could use the light to read by. From that time on, if there were fireflies around, he would use them as a lamp to study by. Due to all his diligent studying, and hard training, he became a senior official later on in his life.

The idiom "Light reflected by snow or collected from fireflies" is now used to indicate those who study hard in difficult circumstances.