When William Shockley proposed the bipolar transistor theory, nobody knew how to build such a device and the announcement about the transistor’s invention in late 1948 by Bell labs did not evoke any public or professional interest. But now we know that the invention of bipolar transistor led to the beginning of the integrated circuit revolution. Today’s integrated circuits contain more than a billion transistors of nanoscale dimensions, packed into a small area (about 120 mm 2 ) and they have changed the way we live and communicate with each other. Integrated circuits contain both active devices, such as transistors, and passive devices – resistors ( R ), capacitors ( C ) and even inductors ( L ). We are so familiar with these three passive circuit elements that none of us ever thought that there could be a fourth circuit element other than R , L and C .
In 1971, a little known professor, Lean Chua, working at University of California, Berkeley, published a paper in the IEEE Transactions on Circuits Theory , postulating the existence of a fourth circuit element, in addition to those which we all know  . Chua named this element memristor. He even suggested that we may have to rewrite the circuit theory books, due to the existence of this fourth circuit element. No one actually paid any serious attention to this basic scientific discovery because there was no physical example or model for a memristor. However, in an article in Nature , when a group of scientists from Hewlett-Packard announced in May 2008 that they had built a prototype of a memristor and that its operation could be understood using a simple physical model, it led to a frenzied interest in Chua’s work and his memristor  . The objective of this editorial is to provide a brief outline of this fourth circuit element, its operation and possible applications, so that we can appreciate why there is so much of interest in this scientific discovery.
You can read the complete article at http://tr.ietejournals.org/text.asp?2009/26/1/3/48462