Transfection commonly refers to the introduction of nucleic acids into eukaryotic cells, or more specifically, into animal cells. Classically, the term transfection was used to denote the uptake of viral nucleic acid from a prokaryote‑infecting virus or bacteriophage, resulting in an infection and the production of mature virus particles. However, the term has acquired its present meaning to include any artificial introduction of foreign nucleic acid into a cell.