If you thinking this building is at fire then you are totally wrong. Actually it's a real cloud, made by Architect Testuo Kondo has teamed up with climate engineering company Transsolar to fill a building with clouds at the Venice Architecture Biennale.
Its made up of microscopic water droplets kept in closed building. These clouds are created by pumping three layers of air at different temperature & humidity levels & by using machine the reaction was made to create clouds. It looks very naturally & cool. have a look at video below