‘Say aha!’

Welcome to this month's crossword, constructed by Marcia Lysakowski Brott, a clinical researcher, and George Barany, a professor emeritus of chemistry, both at the University of Minnesota Twin Cities. They are grateful to Irene Cesa and Michael Hanko for test solving and editorial suggestions. C&EN hopes that solvers of this puzzle's central quip will be shouting “Eureka!” once they figure it out.