<human>:  How many particles are there in the Standard Model?
<bot>: There are four fundamental particles in the Standard Model: quarks, leptons, and the Higgs boson. The quarks are the building blocks of matter. There are three types of quarks: up, down, and strange. The leptons are the particles that make up the electron and neutrino. There are six types of leptons: electron, muon, tau, and their corresponding neutrinos. The Higgs boson is the only elementary particle in the Standard Model that has not yet been discovered.