A number of particle models that are suitable for simulating multiphase fluid flow and biogeochemical processes have been developed during the last few decades. Here we discuss three of them: a microscopic model - molecular dynamics; a mesoscopic model - dissipative particle dynamics; and a macroscopic model - smoothed particle hydrodynamics. Particle methods are robust and versatile, and it is relatively easy to add additional physical, chemical and biological processes into particle codes. However, the computational efficiency of particle methods is low relative to continuum methods. Multiscale particle methods and hybrid (particle–particle and particle–continuum) methods are needed to improve computational efficiency and make effective use of emerging computational capabilities. These new methods are under development.