Laboratory animals are essential tools of biomedical research including modeling neurodegenerative diseases. For their optimal use, not only selection of the most suitable species but also adequate genetic and gnotobiological category and maximum and standardized quality are essential. The main factors determining standardized quality as well as welfare of the animals are optimum environmental conditions in the animal facility specific for each species. The chapter describes the basic categories of laboratory animals from the perspective of genetics and gnotobiology and discusses both their advantages and limitations. Currently used conventional, barrier, isolator and individually ventilated cages housing technologies are described. Ethics of animal experimentation principles of which are known as reduction, replacement and refinement (3Rs) but include also providing the animals with optimum living conditions and welfare is also addressed.