In this week's Science, researchers from the Synthetic Yeast genome Project — who previously reported constructing a single yeast chromosome — publish seven studies detailing the creation of five more, a major step toward the creation of the first fully synthetic complex organism. The first five studies describe the assembly of yeast chromosomes synII, synV, synVI, synX, and synXII, while a sixth paper describes the procedures and goals of creating a fully synthetic eukaryote genome for baker's yeast. A seventh paper offers a look at the three-dimensional structure of various synthetic chromosomes, including strains with more than one synthetic chromosome. A perspective piece provides context for the work, which could lead to the creation of "designer organisms" that could be used to understand human disease, identify new drug targets, and generate new therapeutics.