In America, at least 17 people a day die waiting for an organ transplant. But instead of waiting for a donor to die, what if we could someday grow our own organs?

Last week, six years after NASA announced its Vascular Tissue Challenge, a competition designed to accelerate research that could someday lead to artificial organs, the agency named two winning teams. The challenge required teams to create thick, vascularized human organ tissue that could survive for 30 days.