It has been fancifully dubbed the angel of creation and, to the particular scorn of physicists, the god particle.
The Higgs Boson is said to have appeared out of the chaos of the Big Bang 13.7 billion years ago and turned the flying debris from that primeval explosion into galaxies, stars, and planets.
Its formal discovery, according to a broad scientific consensus, would be the greatest advance in knowledge of the universe in decades.
But until now, in the four decades of research since its existence was first posited, no-one has claimed to have more than seen a hint of the Higgs Boson.
This may be about to change.
On Wednesday at the CERN particle physics research centre near Geneva, two separate teams of "Higgs Hunters" - a term they profess to hate - may well announce they have spotted it.
Or at least something that looks incredibly like it.
"Think of it as a smoking duck," says Oliver Buchmueller, a senior scientist on one of the teams, the CMS.
"If it walks like a Higgs and it quacks like a Higgs, then we would have to at least consider the possibility that we have a prominent new member of the Boson family on our hands."
The Higgs Boson is a vital component of the "Standard Model" - the all-encompassing 30-year-old scientific theory of how the universe works at the simplest level.
Without it, says U.S. physicist Matt Strassler, "nothing like human beings, or the earth we live on, could exist".
WHY A BOSON
Why is it called a boson? Because elementary particles, the building blocks of the cosmos, come in two types - bosons and fermions - and the Higgs has been assigned to the first.
Physicists say the particle is like a wave from what would be the otherwise invisible Higgs field and would provide prime evidence that that underlying force is there.
Buchmueller, like all scientists at CERN, is silent on what might be revealed on July 4 by scientists who have analyzed the product of many trillions of mini-big bangs created over the past two years in CERN's Large Hadron Collider (LHC).
"We will all just have to be patient till Wednesday," says Pauline Gagnon, a Canadian physicist on CMS' rival team Atlas, blogging from a big particle physics conference in Australia.
Last December, CMS and Atlas told a similar seminar at the sprawling CERN campus on the Swiss-French border, that they had seen "tantalizing glimpses" of what could be the boson, named after 82-year-old British theoretical physicist Peter Higgs.
Since then, power in the underground LHC has been ramped up and the rate of almost light-speed particle collisions in it has been tripled in an attempt to produce something more definite.
A sense that "something" has been seen has been bolstered not only by the announcement of the CERN seminar and a live video feed to the Melbourne congress but by other linked events scheduled around the globe.
New York's Columbia University said it was holding an early-hours pajama party in the hope of seeing "sub-atomic fireworks".
VARIOUS FORMS
In London, a concert hall across from the Houses of Parliament has been booked for a similar, but daytime, event. Japanese, Russian and Chinese scientists will be watching too.
At the U.S. Fermilab near Chicago, where scientists spent three decades looking for the Higgs in their Tevatron collider which was shut down last December as Washington cut off funds, another seminar has been set for Monday.
That gathering, according to the centre's daily bulletin, will hear the final "Higgs results" from the Tevatron, a much less powerful machine than the mighty LHC.
But just what will be announced at CERN - and Fermilab - remains far from clear.
To claim a discovery, scientists have to have a "5 sigma" certainty - or be sure that there is less than a one in a million chance it is a fluke.
The Higgs, both field and boson, could come in various forms, specialists say, and although one type may have been seen it may yet take time to determine exactly which one it is.
The question will probably remain open on whether it is a Standard Model version, or something else that will take scientists into the science fiction realms of "New Physics".
"It could prove to be a single child or have siblings, and what its hair color or genetic code is would remain to be established before we know its true nature," said Buchmueller.
