FreeFem++ is an implementation of a language dedicated to the finite element method. It enables you to solve Partial Differential Equations (PDE) easily. Problems involving PDE (2d, 3d) from several branches of physics such as fluid-structure interactions require interpolations of data on several meshes and their manipulation within one program. FreeFem++ includes a fast 2^d-tree-based interpolation algorithm and a language for the manipulation of data on multiple meshes (as a follow up of bamg). FreeFem++ is written in C++ and the FreeFem++ language is a C++ idiom. It runs on any Unix-like OS (with g++ version 3 or higher, X11R6 or OpenGL with GLUT) Linux, FreeBSD, Solaris 10, Microsoft Windows ( 2000, NT, XP, Vista,7 ) and MacOS X (native version using OpenGL). FreeFem++ replaces the older freefem and freefem+.