nterest of scientists has been deviating since 20th century, from the use of animals intheir experimental work towards substituting with‘Alternatives’, thus reducing the useof live animals in experiments. This‘Alternative’concept is principally the‘Replacement’alternative that was indicated in the book;‘The Principles of HumaneExperimental Technique’written by Russell and Burch in 1959. Although manymethods of replacement have been developed and used by researchers, most of theseare notabsolutereplacement models. As absolute replacement models should notinvolve whole animals and animal tissues, in many instances models used byresearchers arerelative. Relative replacement models include lower vertebrates,invertebrates or animals having lower level of sentience and tissues, cells, sera andembryos etc. of animal origin. These relative replacement models of course reduce orprevent the use of conscious living vertebrates developmental biology, oncology, pharmacology, toxicology, teratology, genetics,neurobiology, environmental sciences, stem cell research etc. [2–6]. Identification ofsubstances/key molecules responsible for regenerative capacity of damaged heartmuscle, retinal tissues of eyes, nervefibers shed light for the scientists one day to focuson new therapies for people with ischaemic heart disease, spinal cord injuries and tocombat degenerative eye disease damage in humans. ZF, specially its embryo model has its wide acceptance and popularity as a replacementmodel due to many scientific attributes such as small size of ZF, ease of maintenance,low cost, rapid growth rate, high fecundity rate, external fertilization, optical trans-parency of the embryo (Figs.1and2), ease of genetic manipulations, high geneticsimilarity to humans and regenerative capacity