The phenomenon of mass migration from China's towns and villages into the big cities has been well documented over recent years, as have issues surrounding the children these workers often have to leave behind.China's State Council has now introduced guidelines aimed at protecting those children who have been left behind in rural areas by one or both parents.So, what are the biggest challenges facing migrant workers' children?What are the key features of the new guidelines?And will they be enough to address this challenging situation?