Superconducting quantum interference devices, or SQUIDs, are highly sensitive instruments used to measure extremely small magnetic fields. They operate based on the principles of superconductivity and quantum mechanics, utilizing a loop of superconducting material with one or more weak links. When exposed to a magnetic field, the current flowing through the loop can change, allowing for precise measurements. SQUIDs are widely used in various fields, including medical imaging and geophysics. Their ability to detect minute changes in magnetic fields makes them valuable for applications such as magnetoencephalography, which studies brain activity, and mineral exploration, where they help locate valuable resources.