The Standard Model consists of 17 elementary particles that fit into a mathematical and theoretical framework that explains matter and forces. Since last century, the model has been able to not only explain, but also to predict existences of undiscovered particles. The particles are categorized into two groups: fermions and bosons. Fermions make up matter. There are two types of fermion: lepton and quarks. Quarks make up neutron and proton, while leptons make up electron-like particles. Both groups contain six particles, which are organized into 3 pairs or “generations.” The first one is the lightest and most stable. Higher generations will not be stable and quickly decay. Bosons, on the other hand, are responsible for transferring forces. There are four types of forces in our universe: the strong force, the weak force, the electromagnetic force, and the gravitational force. Bosons can explain each one except gravity: the strong force is carried by gluon; the weak force is carried by w and z bosons; and the electromagnetic force is carried out by photon. Higgs boson explains why some particles will have mass.
The Standard Model works beautifully as an isolated mathmatical theory. However, it fails to incorporate gravity into its framework, resulting a big issue. Furthermore, the quantum theory behind this model does not seem to fit with the law of general relativity, causing a split between micro and macro world. Most importantly, scientists thought that the model might provide an answer for dark matter, which did not happen. Therefore, although this theory proposes many beautiful solutions, it also creates more mysteries that are not solved.