A man in need of a new heart, an ex-soldier with post-traumatic stress disorder and a woman whose lung problems are man-made. They're all under 30. And they're fighters.

Tsegi can’t breathe like other people. The young Mongolian has severe lung problems - that are man-made: she’s from Ulan Bator, one of the world’s most polluted cities.

Tsegi can’t breathe like other people. The young Mongolian has severe lung problems - that are man-made: she’s from Ulan Bator, one of the world’s most polluted cities.

A man in need of a new heart, an ex-soldier with post-traumatic stress disorder and a woman whose lung problems are man-made. They're all under 30. And they're fighters.