The Guardian's Witness website is asking churches across Britain to upload pictures and videos of their congregations.
From converted units on industrial estates to magnificent medieval cathedrals, Witness is welcoming submissions from congregations of all shapes and sizes.
The aim is to build up a picture of the congregations that fill the nation's churches each Sunday.
"Who are the Christians in Britain today?" says the blurb. "On any given Sunday, there will be at least 2.5m people in churches of various sorts, but each congregation tends to be an island with little contact with others."
City Church Edinburgh, St Peter's Brighton, Greenbelt and Big Church Day Out are among those to have uploaded their photos so far.
Churches have 28 days left to make their submissions.
Visit https://witness.guardian.co.uk/ to add your contribution.
