Infants from a myriad of species attach to their caregiver regardless of the quality of care received, although the quality of care influences development of the stress system. To better understand this relationship, this chapter characterizes attachment learning and the supporting neural circuit in infant rat pups. During early life, odors paired with pain paradoxically produce subsequent approach responses to the odor and attachment. The neural circuit supporting this attachment learning involves the olfactory bulb encoding the preference learning and suppression of the amygdala to prevent the aversion learning. Increasing the stress hormone corticosterone during acquisition or decreasing endogenous opioids during consolidation prevents this odor approach learning. These data suggest that early life attachment is readily learned and supported by both increased opioids and decreased stress.