Viral vectors are tools commonly used by molecular biologists to deliver genetic material into cells. This process can be performed inside a living organism ("in vivo") or in cell culture ("in vitro"). Viruses have evolved specialized molecular mechanisms to efficiently transport their genomes inside the cells they infect. Delivery of genes or other genetic materia by a vector is termed transduction and the infected cells are described as transduced. Molecular biologists first harnessed this machinery in the 1970s. Paul Berg used a modified SV40 virus containing DNA from the bacteriophage λ to infect monkey kidney cells maintained in culture.