Restriction Enzymes or Restriction Endonuclease are enzymes which act or break larger DNA molecule into shorter fragments at specific nucleotide sequence. In this manner, they help in isolating DNA fragments from parent DNA molecules. They were discovered by Arber, Nathans and Smith. W Arber first postulated the existence of restriction enzymes in early (1960), Smith (1970) first isolated a restriction enzyme (called Hind-II at present) from the bacterium Haemophilus influenza and Nathans (1971) elaborated work of Smith. Alexander Flemming discovered first antibiotic penicillin from Penicillium notatum. Waksman (1945) discovered antibiotic streptomycin and coined the term antibiotics.