This chapter outlines factors to be considered in investigating the seed biology of CWRs, both from the point of view of effectively utilizing the seed soon after collection and of ensuring the seed remains viable for utilization following long‐term storage. Seed collections are initially assessed for seed fill, viability, and germinability. When monitoring seed viability in ex situ collections, it is important to use consistent treatments and test conditions. The effectiveness of a particular seed storage method in maintaining viability and maximizing longevity is dependent on the seed's response to reduced seed moisture content (MC) and reduced temperature. Seed longevity also varies between species, and understanding species differences in seed longevity is critical to the effective management of ex situ collections of both crop and wild species. Significant new resources are now available for both collection and development of technologies, namely, in vitro and cryopreservation, for long‐term storage of seed.