Kari Alitalo, a scientist at the University of Helsinki in Finland, wanted to develop a more precise map of the lymphatic system, which carries immune cells throughout the body and removes waste and toxins. To do this, he used genetically modified mice whose lymphatic vessels glowed when illuminated by a particular wavelength of light, as they had received a gene from a species of glowing jellyfish. When viewing the modified mice under the light, something unexpected was seen… the heads of the mice glowed.
This was surprising because it had been accepted wisdom for more than 300 years that the lymphatic vessels did not extend into the brain.
In the 21st century, major findings involving basic human anatomy are rare.