Introduction The aim of this text is threefold: Firstly, to prove to the Teacher that the author of this article (i.e. Student) have sufficiently internalized all the facts presented during UE Neuroimagery. Secondly, Student aims to introduce the notion of «invasivity» as something which should be considered wery seriously by someone who seeks an «ideal method» of conducting his future (neuro)scientific experiments towards success. But the ultimate aim si to show that certain «philosophical schools» who point out to «invasivity-related aspects» of current neuro-scientific research are not doing so from the position of moralizing savants locked in their ivory towers, but they do so because of concrete and highly-pragmatic reasons related to purest expressions of highest scientific practice. Principal thesis of this text states that « invasivity » and « reversibility » aspects of a chosen experimental method should determine experimentator's choice at least as significantly as other aspects like spatial/temporal resolution characteristics, signal/noise ratio or economical feasibility. First part of the text is dedicated to highly invasive techniques tissue extraction and analysis by means of electron, multiphoton or confocal microscopes. Post mortem autopsy and chirurgical interventions like vivisesction or lobotomy will be mentioned when discussing this group. Common demoninator of these approaches is that their condition sine qua non of their realisation is nonreversible and fatal degradation of one vital functions of the organism under study or...death. Second part of the text is dedicated to somewhat more reversible, nonetheless still very brutal «in vivo» techniques like that of calcic imaging, optic imaging or electrode implantation. Because it is evident that such approaches can inflict severe injuries and suffering of the organisms under study, they will be labeled as «partially reversible quasi in vivo techniques». Contrary to common categorisation of these days, even techniques like PET (positron emission tomography) or X-ray imaging will be included into this middle group of partially invasive techniques. This is due to their high-energy kinship with radioactivity which can without any doubt induce mutations resulting in the disequilibrium of a living system which is commonly known as «loss of health». The loss of this precious equilibrium is the reason why we'll include all the luminescence/fluorescence marker techniques into this category as well. The third part of the text aims to bring hope. It will be fully devoted to techniques which can be considered as fully reversible: focus will be definitely on Magnetic Resonance Imaging (MRI) and Electroencephalography (EEG) while other non-invasive techniques (NIRS, echography or TCD) will be excluded from the list due to lack of Student's personal experience with these techniques. The small part of this final part will be dedicated to «what if?» speculation proposing to use these pure and elegant techniques not only for imaging, but as well as a tool of healing practice. These three parts can be considered as a core of Student's homework demanding him to «highlight the advantages and limits of these techniques depending from the scientific question You'll pose». The question posed by student is this: «According to what criteriae could we possibly quantify invasivity of an experimental tool or method ? » This text will try to answer this question by introducing the term which we label hereby as «Information/Invasivity Quotient» (IIQ).We'll analyse this notion from more ethical perspective in Discussion section,while Appendix will summariz IIQ-based ranking of 4 presented methods.