A biopsy is a medical procedure in which a small sample of tissue or cells is removed from an organ, body part, or lesion for examination under a microscope. This can help to diagnose diseases such as cancer, and determine the severity of conditions like fibroids or cysts. Biopsies are commonly performed using a needle or during surgery, depending on the location and size of the tissue being sampled. The procedure may cause some discomfort or pain, but is generally safe when done by an experienced healthcare professional.