Seed development and maturation are tightly regulated processes governed by complex gene expression networks controlling cellular differentiation, nutrient deposition, desiccation tolerance, and dormancy. This chapter synthesizes current knowledge on transcriptional dynamics from embryogenesis to the fully matured seed, highlighting the roles of key transcription factors such as Leafy Cotyledon (LEC), Abscisic Acid Insensitive (ABI), and Fusca (FUS). The modulatory effects of plant hormones— including abscisic acid, gibberellins, and auxins—are discussed in the context of seed filling and maturation. Advances in transcriptomic tools, particularly RNA sequencing (RNA-seq), have facilitated high-resolution, stage- and tissue-specific profiling, revealing novel genes and networks involved in storage protein synthesis, lipid biosynthesis, and protective mechanisms. Epigenetic regulation, through DNA methylation and histone modifications, adds further refinement to developmental control. Environmental factors and maternal influences are examined for their impact on gene activity and seed phenotype. Understanding these regulatory frameworks offers practical avenues for crop improvement, targeting enhanced nutritional quality, stress resilience, and storage longevity. Future integration of genomics with proteomics and metabolomics holds promise for unraveling the molecular complexities of seed biology and advancing sustainable agriculture.