In a human crowd or in a shoal of fish, thousands of individuals
interact and form large scale structures. Although the interaction among
individuals might be simple, the resulting dynamics is quite complex.
Modeling is an essential tool to understand such dynamics. For instance,
Agent-based models, also referred to as microscopic models, are widely
developed to analyze various dynamics such as swarming and opinion
In this talk, we investigate the emergence of macroscopic behavior
for such models. The challenge is to link "microscopic models"
describing each agent with "macroscopic models" describing the
evolution of a fluid. To achieve this transition, we present a novel
approach based on kinetic theory and asymptotic analysis. Numerical
simulations are presented to illustrate the results.