Models come in many scientific guises — for example, a simplified description of a complex cellular process can form a testing model for experimental research. In addition, structural biologists work with three-dimensional (3D) models of single molecules and molecular complexes, and relatively simple organisms such as yeast are often used as biological models of more complex ones.

So, simplification is the key to studying complex biological problems. One way to understand how cellular initiator proteins function in initiating DNA replication is to appreciate in some detail how viral initiator proteins work, as suggested by Arne Stenlund on page 777. This approach makes sense, because viral initiator proteins seem to be conserved and our current knowledge of viral initiators is more advanced. So, new insights into the viral replication-initiation process provide a model for how more complex cellular initiator proteins might work.

On page 757, Birthe Fahrenkrog and Ueli Aebi describe a 3D reconstruction of the nuclear pore complex that has been created on the basis of electron-microscopy data. This model of the complex machinery that forms the gateway between the nucleus and cytoplasm highlights new structural features and provides new mechanistic insights into nucleocytoplasmic transport.

Model organisms have become indispensable for studying biological phenomena. However, it is easy to forget that the degree of insight that is achieved is dependent on the model organism used. On page 798, Pierre Golstein, Laurence Aubry and Jean-Pierre Levraud remind us of the classical model organisms that are widely used to study programmed cell death. They also make a case for the use of alternative model organisms that might unveil new molecular pathways of apoptotic, as well as other types of, programmed cell death.