Wide binary systems are broken apart. Close binary stars coalesce into single remnants. Stellar remnants within galaxies interact over many many orbits. Others lose energy and sink towards the center. These coalesce into a Supermassive Black Hole.
Protons decay into electrons, positrons, to neutrinos.
All matter not in Black Holes comes apart. Black Holes slowly evaporate by emitting particles and photons via Hawking Radiation. Only matter is a thin, formless gas of electrons, positrons, neutrinos. Increasingly redshifted photons. Some say the world will end in fire.