In many engineering problems, physical phenomena could occur at different length and time scales and they are almost impossible to be described by a single mathematical model. More importantly, in such problems, small-scale physical phenomena could dramatically change macroscopic properties of the system. Over last few decades, particle-based methods have become a powerful tool that allows to model concerned physical phenomena at any length and time scales. In this talk, I’ll introduce some widely-used particle-based methods and share some of my experience in development of particle-based mathematical models for engineering problems.