 Notably he hosted Richard Feynman at Caltech when the physicist studied molecular biology, leading Feynman to remark that Charlie was “...the smartest guy I know”.He was instrumental in the discovery of V(D)J recombination, bacteriophage genetics as part of the phage group and co-discoverer of the amber-mutant of the T4 bacteriophage that led to the recognition of stop codons.The amber mutants discovered by Charles Steinberg in collaboration with Richard Epstein provided a unique opportunity to study the function of virtually all the genes of phage T4 that are required for growth of the phage under laboratory conditions.