What was the difficult technique you used on a single cell at a time?

Question: What was the difficult technique you used on a single cell at a time?
- Keywords:
  cells,
  experiment,
  technique
Asked by werewolvesrock2002 to John on 12 Mar 2014.
- John Foster answered on 12 Mar 2014:
  
  Hi,
  
  The difficult technique was called electrophysiology.
  
  It involved moving a tiny glass needle onto the surface of a single cell (I could only see it under a microscope). Then I applied a little suction to break a small part of the cell membrane open. This gave the inside of the glass needle access into the cell.
  
  This glass needle had an wire in it, and there was one placed outside the cells as well. Because cells have channels in their membranes that let ions (charged atoms) through, the electrical properties of cells can change quite a bit. I could use the wires inside and outside the cell to measure which ions were passing in or out of the cell and even what proteins were letting this happen.
  
  At the end I got a graph drawn by a computer that looked a little bit like an ECG monitoring the heart except that it was a single tiny cell that I was measuring electrical changes in!

Question: What was the difficult technique you used on a single cell at a time?