Since its introduction more than 150 years ago, the thought-provoking idea of Maxwell’s demon has profoundly shaped our understanding of the relationship between information and energy. Maxwell’s demon is an imagined microscopic gatekeeper that exploits information at the microscopic scale to produce macroscopic work.

Initially controversial, the demon appeared to challenge a fundamental law of thermodynamics by suggesting that work could be extracted from a system in thermal equilibrium.

Today, this apparent paradox is resolved by recognizing the thermodynamic value of information: Information itself is a physical resource that can be converted into work. This insight has inspired growing interest in information engines—microscopic machines that, unlike conventional heat engines, are powered by information rather than by temperature differences.