Higgs Boson is probably the most sought after un-discovered particle. Currently, the Large Hadron Collider and the Tevetron ar busy trying to find this particle. This particle is thought to hold the whole standard model of particle physics together. (Take the Higgs out of the standard model and all kinds of problems arise like: how do particles have mass?)
Interestingly, the Higgs is best described mathematically as what is known as a scalar field. We've never found a scalar field that actually exists fundamentally! Will the Higgs be the first or will the Higgs turn out to be like the Pion?
The Pion is a particle that "at low energies" is well described by a scalar field. However, fundamentally we have discovered the Pion is actually composed of more fundamental particles called quarks. This composition is pictured above. These quarks themselves are not scalar fields but are fermions best described mathematically by spinor fields. (Not scalar fields)
Reasons like these (plus the fact that the best fit mass for the scalar Higgs, assuming only the standard model, has been ruled out by nearly 2 sigma) have caused many physicists to come up with models where the Higgs is more like the pion: best described as a scalar at low energies but fundamentally a composite particle made up of more fundamental non-scalar particles. Only time will tell.