Quarks and LeptonsBasic building blocks
There are thought to be a few elementary particles which can't be broken down any further and these are mainly Quarks, Leptons and Gauge Bosuns.
Of course it may just mean that our equipment isn't advanced enough yet to further break these particles apart but at present we are fairly confident that these are true elementary particles.
Firstly there's the Gauge Boson. This is basically the means of transmitting the energy that comes from the four forces - for example the actual method by which a magnet exerts an attractive force on a drawing pin or whatever is thought to be by an exchange of massless, virtual particles. In the case of the magnet that would be the gauge boson that relates to electromagnetism, the photon.
Next we have Leptons.
These are very elementary particles, the most commonly recognised one being the Electron. What differentiates Leptons from Quarks is that Quarks are affected by all four forces but Leptons are affected by only three and not the one called the Strong Nuclear force. This allows them to move more freely and interact with other things more easily.
There are six Quarks in total but only two main Quarks, which make up almost everything. They are the Up Quark which has an electrical charge of +2/3 and the Down Quark that has a charge of -1/3.
A Proton consists of 2 x Up Quarks and 1 x Down Quark whilst a Neutron is 2 x Down Quarks and 1 x Up Quark and that's why a Proton ends up with a final charge of +1 whilst a Neutron has no charge at all as 2 Down Quarks (2 x -1/3 = -2/3) is cancelled out by the 1 Up Quark (+2/3)
There are also two anti-quarks which are exactly the same as above but with their charges reversed, so you get an Anti-Up and an Anti-Down
The Up and the Down Quarks are the most common ones we find simply because the other 4 Quarks and corresponding 4 anti ones - Strange, Bottom, Top and Charm, tend to quickly decay into the lighter Up and Down ones.
The heavier 4 were really only found in the first few micro seconds of the Big Bang and can only be seen now in particle collisions such as happens in the LHC. The Top Quark is currently of particular interest as it is very very heavy compared to the others and in fact is nearly as heavy as gold. It's thought that this may be related or at least help us locate the missing 'Higgs Bosun' field - which is the force thought to provide mass to particles.
This is the name given to the theory of 'everything'. Unfortunately it's not quite complete because so far we have to completely leave out gravity, dark matter and dark energy for it to all add up (as well as include the elusive Higgs Bosun in the calculations), but at least it's a measure of the stage of understanding that we have currently achieved.
In the diagram to the left you can see the fundamental components of everything. The 6 Quarks are coloured purple whilst the complementary Leptons are in green. The final column of y g z w are the forces which interact with the others to complete any kind of atom or action.
Reading down the way you can see the 3 fundamental sates of matter, with the number 1 being the most common throughout the universe - ie' Up and Down Quarks combined with Electrons and Neutrinos.
The Standard model holds up very well in all manner of calculations provided the undetermined Higgs Bosun is factored in (which is why scientists are quite confident of eventually discovering it in the LHC). However if the Higgs can't be determined or is proven not to exist then the Standard Model would be immediately redundant - so it is an exciting time for physicists.
Even if the Standard Model survives there is still the very tricky question of Gravity, which you can see is not currently included in the diagram simply because it cannot be made to fit with the equations and so is still a mystery to be solved.
So everything is still wide open at the moment and it's extremely possible that we are still a long way off a true understanding of the universe...
Note: The Standard Model has taken another blow recently as some scientists appear to have discovered that Neutrinos do actually have mass and are not zero mass as the Model suggests...