present study aims to investigate the impact of selenium on the morphological, biochemical and ultrastructural changes in the testes, ovaries and livers of mothers rats and their 14 days old age neonates by transmission electron microscopy. Female rats were dosed orally with distal water and 0.5, 1.7, and 6.0 mg Se/kg bw/day as (10 - 45) nm SeNPs, for 14 days old age neonates. At doses of 1.7 and 6.0 mg Se/kg bw/day,  a lowering in body weight gain was recorded as compared with the control group. Decrease in Glutathione peroxidase (GPX) of moderate dose (MD) and high dose (HD) groups was explained as due to increase reactive oxygen species in body tissues. There was increase in oxidative status (GPX) of Low Dose (LD) comparing to control group. There were no histological changes in the liver, ovary and testes of the investigated neonates at LD , MD and HD groups. The toxicity of Se NPs on oxidation status and ultrastructure of ovaries and testes did not occur at low levels 0.5 mg Se/kg but appear with degrees of changes at high level Se NPs(1.7 – 6.0 mg Se/kg). The present results indicated that Se NPs were not toxic at supra-nutritional levels and can induce a positive effect on both neonate rats health at a dose of 0.5 μg Se/kg-bw and in mother rats growth, whereas the chronic toxicity will be induced by more than 1.7 μg Se/kg-bw.