[dwhly]

Unless the molecular weight is about 10 pentillion (?) you ain't gonna see diddly! Avogadro's number is a big thing. (6 x 10^23). Now agreed that you don't need a mole of something (especially w/ a high molecular weight) to be able to see it in a microscope. But it's probably at least w/in 4 to 5 orders of magnitude of the right number.

[drjesusphd]

DNA is a molecule, and under the right conditions, you can see it under a microscope as chromosomes.

[pmalynin]

Only when it is highly condensed. In ordinary conditions you need something like xray crystallography.

[kghose]

Right, only during cell division and you need the right stain.

[chc]

If you mean 10^18, it's a quintillion.