What is the origin of the idiom "burn the midnight oil" and when to use it?

The idiom "burn the midnight oil" has its origins in the literal act of burning oil lamps or candles to work late into the night. Before the advent of electric lighting, people relied on oil lamps for illumination. Those who continued working long after sunset would need to burn oil late into the night to extend their working hours. Over time, this literal practice evolved into a metaphorical expression, signifying the act of working or studying late into the night to meet deadlines or complete tasks.