A nuclear receptor is a type of protein found inside cells that helps regulate gene expression. These receptors can bind to specific molecules, such as hormones like estrogen or thyroid hormone, and then interact with DNA to control how genes are turned on or off. This process is crucial for many bodily functions, including development, metabolism, and reproduction. When a nuclear receptor binds to its target molecule, it changes shape and moves to the cell's nucleus, where DNA is located. By attaching to specific regions of DNA, nuclear receptors can influence the production of proteins that are essential for various cellular activities, making them vital for maintaining health.