Television news refers to disseminating current events via the medium of television. A "news bulletin" or a "newscast" are television programs lasting from seconds to hours that provide updates on world, national, regional or local news events. There are numerous providers of broadcast news content such as NBC, CNN or Fox News, as well as numerous programs that regularly provide this content such as NBC Nightly News. Television news is very image-based, showing video footage of many of the events that are reported; still photography is also used in reporting news stories, although not as much in recent years as in the early days of broadcast television. Television channels may provide news bulletins as part of a regularly scheduled news program. Less often, television shows may be interrupted or replaced by breaking news reports ("news flashes") to provide news updates on events of great importance.