Countries , international organizations , civil societies , and corporations are allowed to participate .
The theme of the Expo must address a precise challenge , e.g. Future Energy ( Expo 2017 Astana ) , or Living Oceans and the Coast ( Expo 2012 Yeosu ) .
Countries , international organizations , civil societies , and corporations are allowed to participate but the theme of the Expo must address a precise challenge , e.g. Future Energy ( Expo 2017 Astana ) , or Living Oceans and the Coast ( Expo 2012 Yeosu ) .