How do we know what the Milky Way actually looks like when we're inside it? NOVA's Kevin Jiang asked Mark Reid, Senior Radio Astronomer at the Harvard-Smithsonian Center for Astrophysics. For more with Mark Reid on the Milky Way, check out the Q&A on NOVA's blog, Inside NOVA: http://www.pbs.org/wgbh/nova/insidenova/2012/06/mapping-the-milky-way-from-the-inside-out.html