The Wonder Weeks represents a specialized parenting application that translates decades of developmental psychology research into practical guidance for new parents. Based on research originating from Jane Goodall's chimpanzee observations in 1971 and subsequent human infant studies, the app tracks 10 predictable mental development leaps occurring during the first 20 months of life. This scientific foundation distinguishes it from conventional baby-tracking applications that focus primarily on feeding and sleep patterns. The application's core functionality centers around a detailed developmental calendar that predicts when babies will experience 'leaps' - periods of increased fussiness and clinginess associated with cognitive development. For each leap, the application provides comprehensive information about what developmental changes are occurring, typical behaviors parents might observe, and appropriate activities to support the baby's new skills. The system includes milestone tracking, personalized insights based on the baby's due date, and a library of developmental games and activities tailored to each leap phase. User experience demonstrates thoughtful design with an intuitive interface that prioritizes accessibility for sleep-deprived parents. The dashboard clearly displays the current leap phase, progress through developmental stages, and provides daily tips. Real-world usage patterns show parents typically check the app during periods of unexplained fussiness or when seeking developmental activity ideas. The notification system alerts parents to upcoming leaps, allowing them to anticipate and understand behavioral changes rather than reacting with concern. User feedback consistently highlights the app's accuracy in predicting developmental phases and its calming effect on parental anxiety. Reviewer CoraLW123 noted on July 4, 2025 that the app provided crucial support during overwhelming newborn weeks, while FreeMariposa reported on July 3, 2025 that it helped maintain sanity during developmental changes. Multiple reviewers including r_mitchh and Back up first! specifically praised the app's precision in correlating fussy periods with developmental leaps. The application's primary strength lies in its evidence-based approach to explaining infant behavior, though some limitations exist regarding individual variation in developmental timing. While the leap predictions prove accurate for many infants, parents should remember that development occurs on spectrum rather than strict schedule. The app serves best as an educational tool rather than diagnostic instrument, ideally complementing rather than replacing pediatric guidance. Most effective for parents seeking to understand developmental psychology behind infant behavior patterns.