Tiangong 3 will be the third space station in the China National Space Agency Tiangong programme. Tiangong 1 is currently in orbit, being launched in September 2011.The Tiangong 2 laboratory module is expected to launch in 2013, followed by Tiangong 3 in 2015.
The China Manned Spaceflight Engineering Office published a brief description of Tiangong 2 and 3 in 2008, The core module will be 18.1m long with a maximum diameter of 4.2m, and a mass of 22t, and have a multi-berthing docking module to allow up to four spacecraft to dock simultaneously.
Obviously, detailed information is thin on the ground so this image is based on 'best guesses' and conjecture, but it's expected to have two laboratory modules with their own solar arrays, cargo ships will be able to dock, delivering supplies and equipment, as well as Shenzou spacecraft for crew transfers.
Image appeared "How It Works" magazine.