and the humans. These philosophies underline the important role that families play in Chinese cultures. Besides cultural factors, grandparents taking care of their grandchildren also appears in the context in which their adult children need to work full-time, and the child care services are either too expensive (in big cities) or too scarce (in remote areas). Grandparents serving as their grandchildren's caregiver is particularly common in rural China. Due to the fast development of urbanization in China since the 1980s, up to 220 million migrant workers from rural areas move to urban areas to seek for more job opportunities, which leave around 58 million children behind in rural areas, grandparents, therefore, undertake the role of parents and become caregivers to their grandchildren. A new population named “left-behind grandparents” appears in this context, these grandparents live in rural China, and their main job is to look after their grandchildren, most of these grandparents are facing financial burdens and wish their adult children could come back. The mental and physical health of “left-behind grandparents” needs more attention from the public. Even though in urban areas where child care services are available, nearly all grandparents still prefer to take care of their grandchildren voluntarily. Not only because this can reduce their adult children's financial burdens on child care services but also taking care of their own grandchildren is a more effective way to maintain family harmony. In the US, taking care of grandchildren is not a necessary responsibility of grandparents. Grandparents taking care of their grandchildren is often caused by involuntary events or crisis, and it is more like a solution to a problem, not an initiative desire, which is a distinct difference from that in China. For example, grandparents in the USA often take care of their grandchildren when their adult children get into troubles such as substance abuse, incarceration or parental death. Differences also exist in different ethnicities in the US. Caucasian individuals generally regard individual independence as more important, so grandparents are less likely to take care of their grandchildren. However, African American and Latino individuals are more likely to regard looking after grandchildren as a family tradition and are more willing to provide help for their adult children. Ethnic differences in grandparents looking after their grandchildren reflect different cultural values that different ethnic groups hold. To be more specific, African American grandparents are more likely to provide guidance and