More details for those who are interested. The physics package is about the size of a grain of rice. https://www.nist.gov/system/files/documents/2017/05/09/VCA

More details for those who are interested. The physics package is about the size of a grain of rice. https://www.nist.gov/system/files/documents/2017/05/09/VCAT-NIST-CSADemo.pdf https://www.nist.gov/system/files/documents/2017/05/09/VCAT-... Many teams around the world are actively developing improvements on this technology. https://www.nist.gov/news-events/news/2019/05/nist-team-demonstrates-heart-next-generation-chip-scale-atomic-clock https://www.nist.gov/news-events/news/2019/05/nist-team-demo...