Infinitesimal.

I work with solutions so small I can barely see them, let alone suck them into my pipette to mix and redeposit. My strings of little vials contain tiny drops of fluid, and from those I suck ever smaller samples, combining them at concentrations I never thought possible. How in the world can we learn from one microliter of anything? Imagine a drop that fits inside the "o" on this page, and then imagine you can determine the concentration of DNA it holds to two decimal points. Stop imagining. It's not only possible, but commonplace.

The total volume of my experiments over the past week could easily fit inside a toothpaste cap, but they probably cost more than their weight in gold. 4 µl of an isolated polymerase, kept on ice until the last moment. 1.7 µl DNA template from each of my eppendorf capsules. 2 µl dye, one of distilled water, a few of buffer solution, and a few more additions combine to yield no more than 20 µl in any one tube at any given time (equivalent to approximately 5 drops). I hold my tubes to the light so I can see the tiny pools of sample barely covering the pointed, plastic apices.

The juxtaposition of my lab work with my class work never fails to make me laugh. This morning, I pipetted barely-there DNA isolations and the toxic carcinogen ethidium bromide. This afternoon in chem lab, I weighed out a mole of pennies. Wow. I'm incredibly grateful I have my lab work to keep my interest.