Still with the blue mood.
These clouds over Leicester in England are called 'noctilucent' clouds, Latin for 'night-shining' and are usually seen over the polar regions.
They form at an altitude of around 55 miles which is called the mesosphere and are made up of tiny ice crystals which are illuminated by the sun below the horizon.
These clouds have been photographed in Antarctica where they are having an effect on the ozone layer.
NASA launched a satellite in 2007 to study these clouds. There are three instruments on board, one takes pictures of the clouds, another measure the temperature of the mesosphere and how much water vapour and other gasses are present and the third sees how much dust from meteors enters Earth's atmosphere.