A growing number of people--immigrants, refugees, asylum-seekers, displaced individuals, and families--lead lives that transcend national boundaries. Often because of economic pressures, these individuals continually move through places, countries, and cultures, becoming exposed to unique risk and protective factors. Though migration itself has existed for centuries, the availability of fast and cheap transportation as well as today's sophisticated technologies and electronic communications have allowed transmigrants to develop transnational identities and relationships, as well as engage in...