Functional Magnetic Resonance Imaging (fMRI) is a technique used to measure and map brain activity. It works by detecting changes in blood flow. When a part of the brain is more active, it uses more oxygen, and blood flow to that area increases. The fMRI scanner can detect these changes and create detailed images showing which parts of the brain are involved in specific tasks. For example, if someone is solving a math problem, fMRI can show which brain areas are working harder during that activity. This helps scientists understand how different parts of the brain contribute to various mental functions.