I 'cut and pasted' this together before, just to try to remember myself how 'it' worked.

And now I share it with you:)

"

The Pauli exclusion principle is a quantum mechanical principle formulated by Wolfgang Pauli in 1925.

In contrast to bosons, which have Bose-Einstein statistics, only one fermion can occupy a quantum state at a given time.

Three types of particles from which ordinary matter is made—electrons, protons, and neutrons—are all subject to it.

In the Standard Model there are two types of elementary fermions: quarks and leptons.

In total, there are 24 different fermions; 6 quarks and 6 leptons, each with a corresponding antiparticle.

The Pauli exclusion principle helps explain a wide variety of physical phenomena.

One such consequence of the principle is the elaborate electron shell structure of atoms.

And of the way atoms share electron(s) - thus variety of chemical elements and of their combinations (chemistry).

An electrically neutral atom contains bound electrons equal in number to the protons in the nucleus.

Since electrons are fermions, the Pauli exclusion principle forbids them from occupying the same quantum state.

So electrons have to "pile on top of each other" within an atom.

Bosons are particles which obey Bose-Einstein statistics.

And in contrast to fermions which obey Fermi-Dirac statistics, they can occupy the same quantum state.

Thus, bosons with the same energy can occupy the same place in space.

Therefore bosons are often force carrier particles while fermions are usually associated with matter.

Although the distinction between the two concepts (Boson/Fermions) isn't clear cut in quantum physics.

The observed elementary bosons are all gauge bosons: photons, W and Z bosons and gluons.

A Bose–Einstein condensate (BEC) is a state of matter of bosons confined in an external potential and cooled to temperatures very near to absolute zero (0 K, −273.15 °C, or −459.67 °F). Under such conditions, a large fraction of the atoms collapse into the lowest quantum state of the external potential, at which point quantum effects become apparent on a macroscopic scale.

The result of the efforts of Bose and Einstein is the concept of a Bose gas, governed by the Bose–Einstein statistics.

Which describes the statistical distribution of identical particles with integer spin, now known as bosons.

Bosonic particles, which include the photon as well as atoms such as helium-4, are allowed to share quantum states with each other.

Einstein demonstrated that cooling bosonic atoms to a very low temperature would cause them to fall (or "condense") into the lowest accessible quantum state, resulting in a new form of matter. "

Taken from those three

http://en.wikipedia.org/wiki/Fermionshttp://en.wikipedia.org/wiki/Bosonhttp://en.wikipedia.org/wiki/Bose-Einstein_condensateand for a description of the phenomena of BEC fluids.

http://en.wikipedia.org/wiki/Bose-Einstein_condensate#Discovery