Crop plants often have large and complex genomes; the maize genome, for example, is around 2.5 gigabase pairs (109 base pairs), approximately the same size as that of humans. Richard McCombie (Cold Spring Harbor Laboratory, New York, USA) described the remarkable progress being made in maize genome sequencing at Washington University in St Louis by Richard Wilson and colleagues. Their strategy is to sequence 19,000 bacterial artificial chromosome clones (BACs) from the minimal tiling path - the minimum number of overlapping clones that cover the whole genome - to finish the sequence, and to annotate it. One year into the project, 30% of the clones are in the shotgun-sequencing phase and nearly 10% have been finished using capillary-based sequencing.