The biggest wind farm in Europe is getting ready for the final switch on in East Renfrewshire in Scotland.
Around 180,000 homes will be able to get their electricity from the wind farm's 140 turbines.
The farm has cost £300m to build, and the company behind it, ScottishPower Renewables, is hoping to add another 81 turbines to the site in future.
The turbines all stand more than 110m high, and the site covers an area the same size as Glasgow city centre.
Some turbines have been working since January 2008, and Wednesday Scotland's First Minister Alex Salmond will turn the remaining ones on too.
And larger wind farms could be on the way, with a spokesperson for ScottishPower Renewables saying they're hoping to be allowed to build an even bigger one in the sea.
Not everyone's a fan
Keith Anderson said the company wants to build a farm five or six times the size of the one at Whitelee, off the west coast of Scotland.
Not everyone likes the farm though.
The local council objected to the wind farm being built on Eaglesham Moor because of its size and location, but area's local authorities were happy for it to be built.