Conjoined twins is fusion, in which a fertilized egg completely separates, but stem cells (which search for similar cells) find similar stem cells on the other twin and fuse the twins together. Conjoined twins share a single common chorion, placenta, and amniotic sac, although these characteristics are not exclusive to conjoined twins, as there are some monozygotic but non-conjoined twins who also share these structures "in utero". The most famous pair of conjoined twins was Chang and Eng Bunker (Thai: อิน-จัน, In-Chan) (1811–1874), Thai brothers born in Siam, now Thailand. They traveled with P.T. Barnum's circus for many years and were labeled
TWINS TWINS Two Wide-Angle Imaging Neutral-Atom Spectrometers (TWINS) are a pair of NASA instruments aboard two United States National Reconnaissance Office satellites in Molniya orbits. TWINS was designed to provide stereo images of the Earth's ring current. The first instrument, TWINS-1, was launched aboard USA-184 on 28 June 2006. TWINS-2 followed aboard USA-200 on March 13, 2008. Each instrument consists of an energetic neutral atom imager and a Lyman alpha detector. The ENA imager provides indirect remote sensing of the ring current ions, and the Lyman alpha detector gives a measure of the neutral hydrogen cloud about the Earth, known as