Consider a gold microsphere. It is amazing that the several trillion
electrons in the gold can band together and behave like a single quantum,
called a "Plasmon". Such collective creatures are called "Quasiparticles".
Although plasmons were discovered nearly a hundred years ago, it is only
recently that we have begun to appreciate some of their truly extraordinary
properties. One example is a remarkable phenomenon called "Extraordinary
Optical Transmission", first discovered only in 1997. A nanoscale pinhole in
a metal sheet transmits light more than a hundred times more efficiently than
predicted by conventional theory. Many of these extraordinary properties
arise because the plasmon can be thought of as a macroscopic quantum
phenomenon.  "Macroscopic Quantum states" are known to lead to amazing
phenomena ranging from Superconductivity to the thought-provoking
"Schrodinger's cat". An intense effort is now going on to control and enhance
the properties of plasmons for spectroscopy of proteins, DNA binding, and to
Condensed matter physics. Novel optical systems like "Invisibility cloaks"
can also be conceived because of the special properties of plasmons.  We have
shown experimentally that plasmons can be used to enhance the absorption of
infrared light in proteins by several hundred thousand. A brand new field of
Physics called "Plasmonics" has emerged, and it is arguably the fastest
growing field in Physics today. Given the extent of interactions and scope of
applications to both basic Physics and engineering, the Plasmon may indeed be
called "the God Quasiparticle"!