Water is the key element of life, but this element that we thought we knew well may have unexpected properties and might play a role greater than we could imagine in our tree of life. That is the belief shared by the advocates of a surprising theory called “water memory”. For Prof. Luc Montagnier, water has the ability to reproduce the properties of any substance it once contained. Water would have the ability to retain a memory of the properties of the molecules. What if Alzheimer, Parkinson, autism, HIV and even cancer could be treated thanks to this controversial theory?