Note: this site last updated in 2006
An article from "The Molecules of HIV" (c) Dan Stowell
What shape is it? it's pill-shaped, but usually it's fatter at one end than the other. (This is why some people say it's "cone-shaped" - but it's not a recognisable cone. Perhaps "pear-shaped" would be a better description.)
Ordinary cells (such as our own) contain their genome encoded in DNA, and when the DNA code is being used to create proteins for the cell, it is first "transcribed" into RNA - as if some information from a book in a library were being copied onto a piece of paper, so that the piece of paper could be taken away and read elsewhere. HIV and other retroviruses keep their genetic information in RNA form.
Two identical strands of RNA are found in the particle: HIV doesn't necessarily need to have two copies of the RNA, but the RNA molecules are naturally attracted to each other and form dimers (loosely-bound pairs of molecules).
Also attached to the shell (the capsid) are the enzymes which the virus needs to take with it - its protease, reverse transcriptase, and integrase. When a HIV virus particle matures and buds off from the host cell it may also take some "stray" cellular proteins with it - very few sorts of "stray" have been found, including HLA-DR and Beta2-microglobulin.