To measure what's happening in or on a single, living cell, scientists use a technique called the patch clamp which requires an extremely fine pipet held tightly against the cell membrane.
By carefully heating and pulling a small glass or quartz capillary tube, a very fine pipet can be formed. When pulled by machine, the tip will be much smaller than a human hair and the opening on the end of the pipet may be only 1 micron (one-one thousandth of a millimeter) in diameter.
A pipet being hollow, the scientist can either blow or suck on it, depending on the experiment. This is usually done by machine but some scientists do it by mouth. Forcing a squirt of medium makes this very long frog myocyte (right) contract.
To measure cell activity, it is necessary to make good contact between the pipet and cell membrane. This is done by sucking. This single frog myocyte (left) is being picked up by sucking on the pipet. Once good contact is made, it is possible to record ion channels opening and closing.