This document discusses infancy, which is defined as the early period of life and existence as an individual. Key points include that infants in this period first learn to trust caregivers to meet their needs, and it is a sensitive period for brain and body development. Some potential issues during infancy discussed are difficulties from complicated births that can cause brain damage, an unfavorable prenatal environment, issues with parenting like postpartum depression in parents, and unfavorable attitudes towards the infant from significant people like disappointment in the infant's sex or appearance. Discipline is also noted as a potential parenting issue during this period.