We leverage emerging viruses as biological probes to decode early life immunity. Emerging virus pathogenesis, through disruption, can reveal important host immune networks that lead to the discovery of critical host immune functions. Since early immune exposures influence life-long health, deciphering molecular mechanisms associated with fetal immune system development could hold the key for disease intervention even prior to onset. The ultimate objective of our efforts is to describe fundamental immunobiology in order to discover and identify opportunity to improve offspring health outcomes.