1. Introduction

Perspective of "many-particle systems"
[Brady and Bossis, Annu. Rev. Fluid Mech.(1988) vol.20 pp.111-157] 
molecular dynamics
particles : atoms and molecules
interaction : Lennard-Jones, hard-sphere, electrostatic, etc.
Stokesian dynamics (Brownian dynamics)
particles : protein, polymer, colloids, fibers, etc.
(direct) interaction : van der Waals, DLVO, etc.
medium : hydrodynamic and thermal forces
granular dynamics
particles : glass beads, sand grains, billiard balls, etc.
interaction : elastic and inelastic collisions
stellar dynamics
particles : planets, stars, galaxies.
interaction : gravitational force