How many species in our ecosystem have not been discovered? How many words did Williams Shakespeare know but not include in his written works? The unseen species problem has applications in both sciences and humanities, and it has been studied since the 1940s. This classical problem is recently generalized to the unseen features problem. In genomic applications, a feature is a genetic variant compared to a reference genome, and the scientific goal is to estimate the number of new genetic variants to be observed if we were to collect more samples.