In one of my previous lives I pretended to be a crystallographer.
In other words, I would attempt to persuade concentrated protein solutions to get together and form ordered three-dimensional arrays - crystals - so that I could then shoot X-rays at them. The purpose of this was to determine their structure.
One of the things I was taught when I learned crystallography was to be very, very clean. No dust, human hair, bits of glass or other muck were allowed into the experiment. The most frustrating thing about crystallography is that all proteins are different, and will crystallize (if they crystallize) under different conditions, and there doesn't seem to be any pattern to this at all. The lab's insistence on cleanliness was an attempt to factor out one of the variables in the process. But I soon discovered that this may have been counter-productive. As with a lot of things in research, people disagreed with each other and there was a lot of intuition and opinion without a great deal of solid evidence. I realize that this might come as a surprise to some of you, to those who, perhaps, believe that 'scientists deal with facts'. The truth is that at the frontiers of science we don't know what's going on and we're trying to find out - that's why it's called 'research'. If you want facts, look in a text book (and they all contain mistakes, too).
So as I went on and got more experienced, I began to welcome small amounts of crud in my crystallization experiments. In fact, one recalcitrant protein only ever crystallized once, along what looked like an insect leg. I was never able to repeat that experiment; although I did have gothic fantasies about breeding every different sort of insect I could find and using various bodily insect parts as nucleants. A little too Shelley, perhaps.