All the matter we see is made of atoms, whose mass comes almost entirely from their nuclei, which are made of quarks. Quarks, not electrons, represent what we call matter, but particle physics struggles to explain them. For example, their charges come in unexpected thirds for no known reason. Yet they obey the equations of matter, so a model that explains electrons must also explain quarks.
QR4.4.1 A Three-way Interaction
QR4.4.2 Filling a Plane
QR4.4.3 Quark Phases
QR4.4.4 The Strong Force
QR4.4.5 Protons and Neutrons
QR4.4.6 The Weak Force
QR4.4.7 The God Particle
QR4.4.8 Mass and Energy
QR4.4.9 Review