Research on Neighbor Discovery Techniques in Wireless Sensor Networks (WSNs) focuses on enabling sensor nodes to efficiently identify nearby nodes for establishing reliable communication links while minimizing energy consumption and discovery latency. Since WSN nodes often operate with limited power and intermittent connectivity, recent techniques emphasize energy-adaptive and duty-cycled discovery protocols that balance wake-up schedules and idle periods to extend network lifetime. Asynchronous and schedule-based approaches are used to ensure timely discovery without global synchronization. Emerging studies also integrate secure neighbor discovery schemes to protect against spoofing and Sybil attacks, while machine learning and optimization-based methods enhance adaptability under dynamic network conditions. Overall, neighbor discovery remains a fundamental process in WSNs, directly influencing connectivity, routing efficiency, and overall network performance.