For thousands of years, civilizations around the world have built houses out of earth – whether it be mud brick, wattle and dab or rammed earth. But adobe (the practice of making mudbricks) has now become today's "it" building material, from museums around the world designed using adobe, to do-it-yourselfers constructing homes from the very dirt beneath their feet. Correspondent Conor Knighton looks at the history of adobe, and how ancient adobe materials are being merged with 3-D printing techniques.