Imagine walking up to a Star Trek replicator and ordering a bone graft instead of tea, Earl Grey, hot. We're heading in that direction.

The European Space Agency's 3D Printing of Living Tissue for Space Exploration project aims to print human tissue to help injured astronauts heal when they're far, far away from Earth.

Scientists from the University Hospital of Dresden Technical University in Germany bio-printed skin and bone samples upside down to help determine if the method could be used in a low-gravity environment. It worked. ESA released videos of the printing in action.

The skin sample was printed using human blood plasma as a "bio ink." The researchers added plant and algae-based materials to increase the viscosity so it wouldn't just fly everywhere in low gravity.

"Producing the bone sample involved printing human stem cells with a similar bio-ink composition, with the addition of a calcium phosphate bone cement as a structure-supporting material, which is subsequently absorbed during the growth phase," said Nieves Cubo, a bioprinting specialist at the university.

These samples are just the first steps for the ESA's ambitious 3D bio-printing project, which is investigating what it would take to equip astronauts with medical and surgical facilities to help them survive and treat injuries on long spaceflights and on Mars.

"Carrying enough medical supplies for all possible eventualities would be impossible in the limited space and mass of a spacecraft," said Tommaso Ghidini, head of ESA's Structures, Mechanisms and Materials Division. "Instead, a 3D bioprinting capability will let them respond to medical emergencies as they arise."

Some of the raw materials, such as blood plasma, would come from the astronauts' own bodies to protect against transplant rejection.

ESA's project is already looking ahead to adapting the 3D printing of entire organs to space conditions. Just this year we've seen advances in printing a tiny heart from human tissue and a breathing lung air sac.