I suppose the most dangerous ‘experiments’ I do are when I go into brain surgery to take ultrasound data from people having tumours removed from their brains. In this situation, they have a hole in their skull and the covering of the brain (the ‘dura’) removed. I then help one of the surgeons guide an ultrasound probe into the hole and instruct them to gently squash the brain up and down while I acquire data!
I suppose this is pretty dangerous, not just to be careful not to squash too hard, but we must take extra care that everything is sterile before we put the probe on the brain. If it isn’t, it could cause an infection – and the last you want once you’ve reattached someone’s skull is to take it back off again to treat an infection which could have been avoided!