We developed a novel technology to generate liver diverticulum (liver buds) using human induced pluripotent stem cells (hiPSC) by regulating cell-cell interaction, and its clinical application to the treatment for metabolic liver diseases is in progress. In this project, we are working on developing a method to generate a large human liver by adding large blood vessel to hiPSC-liver buds. Under the microgravity condition, positional relation of large blood vessel and hiPSC-liver buds can be easily maintained, so that it could be beneficial to induce tissue-tissue interactions. We developed a novel culture method to assemble hiPSC-liver buds to large blood vessel and successfully verified by the astronaut Soichi Noguchi at 1st space experiment conducted in Dec of 2020. As a next step, we will demonstrate self-organization of hiPSC-liver buds around large blood vessel and examine how gravity affects the growth and functions of human liver.