Homogeneous dynamos in planetary cores and in the laboratory

New developments have occurred in recent years in the field of dynamo theor y. The increase in computer capacity has permitted simulations of convectio n-driven dynamos in rotating spherical fluid shells in parameter ranges muc h closer to those of the Earth's core than has been possible before. The pr ogress in handling flows of liquid sodium in large containers, on the other hand, has opened opportunities for realizations of homogeneous dynamos in the laboratory. These developments will lead to a deeper understanding of t he origin of magnetic fields in planets and in stars.