This Saturday, a giant blue wave will hit Parliament Square at 3pm.
Well actually, first it will assemble around Grosvenor Square at midday and then march through London in support of a safe climate future for all.
Ahead of the UN climate summit in Copenhagen next week, The Wave has been organised by the Stop Climate Change Coalition in support of action on climate change.
It all culminates in the big march on Saturday and tens of thousands of people are going to be there, all dressed in perhaps this link will show you more.
Go the blues.