Yeast nuclei are round, double membrane organelles containing microtubules, and a dark crescent at one end. To biochemically characterize the nucleus and understand the nature of replication and expression of the yeast genome, it is essential to have a method for the preparation of nuclei at different stages of growth. BioIntersect’s Yeast Nuclei Isolation Kit provides a fast and easy method for isolating nuclei from yeast cells. The DNA/protein ratio of the isolated nuclei is 10 times higher than that of whole cells and yields active RNA polymerase enzyme. Nuclei isolated from this method are readily stainable with Giemsa’s, Feulgen’s, and acridine orange methods.