 Richard Smalley, best known for co-discovering the soccer ball-shaped “buckyball” molecule and a leading advocate of nanotechnology and its many applications, was an outspoken critic of the idea of molecular assemblers, as advocated by Eric Drexler.In 2001 he introduced scientific objections to them attacking the notion of universal assemblers in a 2001 "Scientific American" article, leading to a rebuttal later that year from Drexler and colleagues, and eventually to an exchange of open letters in 2003.Smalley criticized Drexler's work on nanotechnology as naive, arguing that chemistry is extremely complicated, reactions are hard to control, and that a universal assembler is science fiction.