Dear Mr. Ahsanullah, the most common electric signature is the cardiogramm, or the encephalogramm. With patch clamp and planar clamp methods you could observe the action potentials and the pico scale ionic currents of a single cell. There is a rising and promising enthousiasm in this area, and actual progress is being done during the last 20 years. You have to specify a bit more, what you are interesting for and what is your goal. 

Hello, you might be interested in some of our recent works:

http://trnres.com/ebookcontents.php?id=242

http://bioed.ufe.cz/doku.php?id=publications

http://www.eurekaselect.com/128777/article

You might find some interesting paper looking at my profile.

Best,

Alberto