In organisms, nanoparticles represent foreign elements with their own physicochemical properties, so they may interfere with the normal physiological mechanisms of the embryos, growing animals and adults. In embryos, NPs sometimes disrupt the development, bringing on malformations which can be lethal due to their small size, can easily penetrate across the cell membrane, avoiding defences mechanism. The chemical composition and physical properties of NPs can be cytotoxic. So NPs then migrate into the cell and reach organelles such as mitochondria, modifying the cell metabolism and provoking cell death, they can interfere with the cell membrane disrupting the membrane functions such as ion transport or signal transduction. The positive electronic charges of NPs can destroy membrane lipid bilayers. Surface coating of NPs can also interfere with cell structure, in vivi and In vitro cultured animals tissues showed that Ag-NPs caused an oxidative stress characterised with well reactive molecules containing free oxygen radicles(reactive oxygen species or ROS), genotoxicity with DNA break or cell apoptosis. An inhibition of Na+/K+ ATPase depending on concentration indicated a default of osmoregulation. At the highest concentrations (100 μg/L). Ag-NPs induced a necrosis of gill lamellae and maximum percentage of individuals died. Ti O2 - NPs provoked DNA damage with or without light.