In 2011, physicist Guy Le Lay stood before a half-filled room on the last day of the American Physical Society’s March meeting in Dallas, Texas, and presented data on a new form of silicon. In his laboratory at Aix-Marseille University in France, Le Lay had grown sheets of honeycombed silicon with layers just one atom thick. He had only preliminary evidence that was unpublished at the time. “It was a risk, you know?” he says now of his decision to present the data. At this year’s meeting, on 18–22 March in Baltimore, Maryland, scientists will deliver about two dozen talks...