A bicycle helmet is a protective headgear designed to reduce the risk of head injuries during cycling. It is typically made of a hard outer shell and an inner foam layer that absorbs impact. Wearing a helmet is important for cyclists of all ages, as it can significantly decrease the severity of injuries in case of accidents. Bicycle helmets come in various styles and sizes to fit different head shapes and preferences. Many helmets also feature ventilation holes for comfort and adjustable straps for a secure fit. Some models include additional features like visors or reflective materials for increased visibility and safety while riding.