The objective of the course is to understand the laws of behaviour and the macroscopic models observed and studied in solid and fluid mechanics from a microscopic description of solids and fluids. The course will provide essential elements to integrate the fact that every body is made up of atoms or molecules interacting more or less strongly into the macroscopic laws of motion. The examples presented in tutorials will illustrate the application of the methods developed in the course. Examples include: carbon nanotubes, elasticity of metamaterials, design of auxetic materials, perfect gases and denser gases.