Scientists have created a groundbreaking DNA-powered computer that can perform calculations using billions of molecules in a tiny drop of water. This system uses the principles of physics and chemistry to compute in a way that is more energy-efficient than traditional computers. Unlike conventional computers that need constant power to force calculations, the DNA computer relies on its "energetically favorable" state — the most stable configuration of molecules — to represent the correct answer. The system, known as the Scaffolded DNA Computer (SDC), was described in a study published in the journal Nature on September 16. The SDC uses short DNA strands that interact with a longer DNA scaffold to perform computations. These strands are placed in a small amount of salt water and then heated and cooled. As the DNA strands interact, they assemble into structures based on programmed rules, effectively performing calculations. The DNA strands behave like molecular puzzle pieces, with their sequences determining how they bind to each other and to specific positions on the scaffold. By designing these binding rules, researchers can "program" different calculations. Each program corresponds to a unique set of DNA strands, allowing the system to be reprogrammed for different computations or inputs. The SDC relies on thermodynamics — the study of energy and how it moves in physical systems — to perform its calculations. When the DNA mixture is heated and cooled, the strands compete to form the most stable, or energetically favorable, arrangement. This final structure encodes the answer to the computation. A single droplet can contain billions, and sometimes trillions, of DNA strands, which interact to produce results. In experiments, researchers demonstrated over 700 computations using the SDC, including addition, multiplication, division, and error correction tasks. While smaller calculations took under a minute, more complex tasks could take up to 14 hours. One of the key advantages of the SDC is its reusability. Unlike many earlier molecular computers that were designed for single-use experiments, the SDC can be used multiple times. Researchers successfully repeated three of the programs up to 24 times and even reran one experiment 1.5 years after the original test. Even when the SDC had partially dried out, the researchers could add water and restart the computations. While the current work is primarily a demonstration of how thermodynamics can be harnessed for computing, future research aims to improve the system’s design for better computation and data storage. Potential applications in DNA data storage are currently speculative, but the study opens new avenues for exploring molecular computing.