Growing greens in zero gravity is the next frontier conquered by China's astronauts.

The Shenzhou-23 crew gave Hong Kong and Macao SAR students a live look inside their "space garden" on Wednesday, showing how lettuce, sweet potatoes and mint thrive without soil, natural rainfall or sunlight.

A specially designed cultivation apparatus provides water, artificial light and ventilation. Harvesting in rounds and keeping the roots intact is the key to growing crops in Earth orbit.