The most striking feature of the igneous rock suite is its compositional diversity and the explanation of this fact is the main goal of igneous petrology. The production, from a relatively homogeneous mantle source of a large range of compositions which go to make up the crust, renders igneous processes of major interest to the earth sciences. Furthermore, magma migration and eruption involve a fascinating range of phenomena making them a rewarding object of study. In this chapter we discuss several aspects of natural convection in fluids and the application of these ideas to the dynamics of magma chambers.