Over the years, HIV has proved a tricky target. No one could definitively show where in the cell it assembled, or when it was released. Certainly no one knew how long it took a single virus to be born. And so much of what's known about HIV and other viruses has been pieced together through experiments that rely on inference: microscopic and chemical probing of cells frozen in different states of viral infection provide only information about what was happening in that cell at a particular moment in time. Now researchers have been able to watch as hundreds of thousands of molecules assemble inside a cell to create a single particle of HIV.

Wow...this is really neat. Scientists have tagged GAG (a major structural protein of HIV) with a fluorescent tag. Using TIRF microscopy (microscopy in which the microscope is able to observe a very thin slice in its focal plane), they were able to do some live cell imaging and show HIV virons assembling REAL TIME! (Be sure NOT to miss the link to the movie, underneath the still image in the article).