The article reviews the critical role of nitrogen (N) in plant growth and development, emphasizing its importance as a fundamental nutrient. It highlights the regulatory mechanisms plants have evolved to cope with different soil N conditions, including N uptake and assimilation. The review discusses the complex regulatory pathways involved in N metabolism, such as nitrate and ammonium transporters, assimilation enzymes, and signal transduction pathways. It also explores the interactions between N and various biological processes, including hormone signaling, microRNA regulation, lateral root growth, drought resistance, anthocyanin synthesis, and mycorrhizal symbiosis. The authors emphasize the importance of understanding these interactions to improve N use efficiency (NUE) and develop strategies for breeding plants with enhanced NUE. The review concludes by discussing future perspectives on improving NUE and reducing environmental pollution from excessive N fertilizer use.The article reviews the critical role of nitrogen (N) in plant growth and development, emphasizing its importance as a fundamental nutrient. It highlights the regulatory mechanisms plants have evolved to cope with different soil N conditions, including N uptake and assimilation. The review discusses the complex regulatory pathways involved in N metabolism, such as nitrate and ammonium transporters, assimilation enzymes, and signal transduction pathways. It also explores the interactions between N and various biological processes, including hormone signaling, microRNA regulation, lateral root growth, drought resistance, anthocyanin synthesis, and mycorrhizal symbiosis. The authors emphasize the importance of understanding these interactions to improve N use efficiency (NUE) and develop strategies for breeding plants with enhanced NUE. The review concludes by discussing future perspectives on improving NUE and reducing environmental pollution from excessive N fertilizer use.