I am old enough to have taken part in the international project to sequence the first eukaryotic genome—that of Saccharomyces cerevisiae—which was released in 1996. Twenty years later, scientists from academic and commercial institutions are now involved in the first wholesale construction of a eukaryotic genome: the Yeast 2.0 Project 1. The construction of whole genomes from scratch is defined as a bottom-up approach in synthetic biology. One of the aims of such work is to reduce genome size and construct a minimal cell factory for industrial applications. These synthetic yeast chromosomes will have unique features to allow scientists to easily reshuffle, eliminate or add new genes 2 in order to engineer cells for efficient production of a desired compound. Synthetic biologists also use a top-down approach to insert functional biological components into natural genomes. This has been used in yeast to produce natural molecules of pharmaceutical value, such as artemisinin acid 3. Currently, many compounds are not chemically synthesized because it is cheaper and more efficient to extract them from plants. The products of synthetic biology could easily replace plants as the source, especially as yeast fermentation is a matter of days, while plants need months or years to grow.