Virus particle budding out from the cell. Although similar to the previous micrograph, the inner core is not as dense and therefore this is an "immature" viron budding out as opposed to a mature virus fusing in to infect a cell.
Magnification including computer enhancements are approximately 100,000 times. A mature round virus particle is sitting next to the cell ready for infection. Note the visible inner core.
Howard Temin, David Baltimore and Renato Dulbecco shared the 1975 Nobel Prize in Physiology or Medicine for the discoveries concerning the interaction between tumor viruses and the genetic material of the cell.