SQUIDs, or Superconducting Quantum Interference Devices, are highly sensitive instruments used to measure extremely small magnetic fields. They operate based on the principles of superconductivity and quantum mechanics, allowing them to detect changes in magnetic flux with remarkable precision. This makes them valuable in various scientific fields, including physics, geophysics, and medical imaging. These devices consist of superconducting loops with one or more weak links, which create interference patterns when exposed to magnetic fields. SQUIDs can be used in applications such as brain imaging (MEG) and particle physics experiments, where understanding minute magnetic changes is crucial for research and diagnostics.