<human>:  How many particles are there in the Standard Model?
<bot>: There are 12 particles in the Standard Model. The Standard Model is a theory that describes the fundamental particles and their interactions. It is the best theory we have so far to describe the forces that bind the known elementary particles together. It is a theory of quantum field theory, which is a branch of physics that studies fields, such as the electromagnetic field, and how they interact with each other.