'Human Flow,' Ai Weiwei's feature-film debut, takes on the global refugee crisis

Ai Weiwei may be China's most famous contemporary artist and a prolific social justice activist. But at his core, Ai insists, he is simply an observer. Not to mention a relentless documenter -- of the Chinese communist government, of international human rights violations, of the 40-some cats that roam his Beijing art studio and of the longtime team members who populate his Berlin art studio, a 150-year-old underground beer cellar. Tonight it's the moon that has captured Ai's attention. He arrived a few hours ago at LAX and now strolls languidly across his agent's Beverly Hills office courtyard, repeatedly stopping to take photos of the sky.