The border wall built during the Trump administration now stands along roughly 190 miles of Arizona's border with Mexico.

Robert Wall is Executive Editor for Defense and Space. Based in London, he directs a team of military and space journalists across the U.S., Europe and Asia-Pacific.

Cell wall articles from across Nature Portfolio The plant cell wall is a complex matrix of linked polysaccharides such as cellulose and pectin, forming a thick semi-permeable rigid barrier outside ...