To experiment is to interrogate Nature by means of various devices, under conditions that allow us to control parameters and obtain reproducible results. It involves gathering together the results obtained and judging whether or not they validate the hypothesis that preceded the experimentation. This experimentation is always associated with the idea that gave rise to it. It takes place within a well defined methodological framework, with well established rules, and it makes use of appropriate instruments. This approach to the understanding of Nature has been christened the experimental method. When applied to the study of living beings, the aim is to decode the mechanisms that govern the functions of organs and of their cells, that is, to decode the laws of Nature.