Re:Dammit, I tried to post a story about this toda (Score 1)

I don't think the size of the structure is that important, although there must be some lower limit.

The definition of what is and isn't alive is a difficult one, some people say the ability for a system to reproduce its self is the only criteria. For instance are viruses alive? (The herpes virus measures only 100 nanometres across} they contain genetic information but can only reproduce inside a host cell.

Plenty of people are working towards creating self reproducing man-made systems and I don't think it will be long before someone succeeds if they haven't already :-)