Rob Martienssen’s special lecture on Barbara McClintock’s ‘Controlling Elements, Then and Now.’ In the 1940s Barbara McClintock famously discovered transposable elements, sometimes called jumping genes, for which she was awarded the Nobel Prize in Physiology or Medicine in 1983. But she called them “controlling elements” and devoted much of her career to the regulation of gene expression, making parallels with bacterial gene regulation, and what we now call the epigenetic control of genome organization.