3D printing human tissue could help keep astronauts healthy all the way to Mars. An ESA project has produced its first bioprinted skin and bone samples. This sped-up clip shows the bioprinting of printing human stem cells using human blood plasma as a nutrient-rich ‘bio-ink’ with the addition of a calcium phosphate bone cement as a structure-supporting material. Plant- and algae-sourced methylcellullose and alginate have been added to increase the viscosity of this bio-ink, to make it suitable for use in low gravity conditions.