Back in 1991, fine artist Marc Quinn, (one of what's now known as the Young British Artists) started the greatest self-portrait project of all time.

Self (blood head) is a self portrait that has been cast and frozen, made out of 4.5 litres of Quinn's own blood, reportedly extracted over a period of about 5 months. And every 5 years, he's updated the the project with a new version.

Over at Marc Quinn's official website, you can view each blood portrait in exquisite detail by zooming in on the heads.

I say this is the greatest self-portrait of all time, not just for the technical mastery and the visceral material they're made in: but because without a 'life-support' system to frame the frozen blood and keep it frozen, these portraits will one day decay. All portraits will decay eventually, whether by weathered erosion of marble or mouldy canvas or tarnished bronze. By crafting these heads out of his own blood, Quinn reconnects us to the the fact that in the fullness of time, no artist's attempt at immortality through self-portraiture will prevail. And of course the series will presumably end in the course of the artist's life, so the artwork's time-dimension has a death of sorts as well.

The Self project is a kind of visual onomatopoeia: a self-portrait, made out of the artist himself, through time. But is it the greatest, most appropriately-done self-portrait that ever will be made?

I don't think so. As the sub-field of science-art known as bioart gains traction, I think we could one day see a self-portrait even closer to an individual artist: giant masses of cultured, extracted DNA perhaps; moulded and animated, a moving person in a tank. A sort of mash-up from Quinn's DNA portrait of geneticist Sir John Sulston and the infamous shark-in-formaldehyde by fellow Young British Artist Damien Hirst. Or perhaps a great-grandchild of a Second Life avatar will appear as the truest, most apt self-portrait of all time.

Or perhaps, wonderfully, something unknown, some technique and vision over our horizon that will shock and attract as beautifully as Self continues to do.