In the present era, Recombinant DNA Technology has brought advancement in every aspect of our lives. In this undergraduate-level book, a brief knowledge of various fundamental elements of rDNA technology like gene cloning, plasmids, fluorescent proteins, cell lines, and cell cultures has been described. The book mainly focuses on the methodology of transforming competent bacterial cells with GFP tagged plasmids. It also discusses the protocol used for the expression of GFP in cultured mammalian fibroblast cells.