Some of the most notable scientific developments in Canada include the creation of the modern alkaline battery and the polio vaccine and discoveries about the interior structure of the atomic nucleus. Other major Canadian scientific contributions include the artificial cardiac pacemaker, mapping the visual cortex, the development of the electron microscope, plate tectonics, deep learning, multi-touch technology and the identification of the first black hole, Cygnus X-1. Canada has a long history of discovery in genetics, which include stem cells, site-directed mutagenesis, T-cell receptor and the identification of the genes that cause Fanconi anemia, cystic fibrosis and early-onset Alzheimer's disease, among numerous other diseases.