Hypothetical technologies are technologies that do not exist yet, but that could exist in the future. They are distinct from emerging technologies, which have achieved some developmental success. Emerging technologies as of 2018 include 3-D metal printing and artificial embryos. Many hypothetical technologies have been the subject of science fiction. The criteria for this list are that the technology: 1. * Must not exist yet 2. * If the technology does not have an existing article (i.e. it is "redlinked"), a reference must be provided for it