The article reviews the advances in genome biology, focusing on the regulatory mechanisms that govern gene expression in mammalian cells. It highlights the role of various biomolecular assemblies in forming structural and regulatory features within the nucleus, which are crucial for transcriptional control. The authors discuss the discovery of cis-regulatory elements (CREs) and non-coding RNAs (ncRNAs) in the genome, emphasizing their importance in gene regulation. They also explore the spatial organization of the genome, including topologically associating domains (TADs), heterochromatin, and euchromatin states, and how these structures influence gene expression. The article further examines the mechanisms of gene regulation, such as de novo recruitment of RNA polymerase II and the role of transcription factors (TFs) in higher-order chromatin assemblies. Finally, it discusses the challenges and future directions in understanding the complex, dynamic, and spatially restricted events that govern gene expression in mammalian cells.The article reviews the advances in genome biology, focusing on the regulatory mechanisms that govern gene expression in mammalian cells. It highlights the role of various biomolecular assemblies in forming structural and regulatory features within the nucleus, which are crucial for transcriptional control. The authors discuss the discovery of cis-regulatory elements (CREs) and non-coding RNAs (ncRNAs) in the genome, emphasizing their importance in gene regulation. They also explore the spatial organization of the genome, including topologically associating domains (TADs), heterochromatin, and euchromatin states, and how these structures influence gene expression. The article further examines the mechanisms of gene regulation, such as de novo recruitment of RNA polymerase II and the role of transcription factors (TFs) in higher-order chromatin assemblies. Finally, it discusses the challenges and future directions in understanding the complex, dynamic, and spatially restricted events that govern gene expression in mammalian cells.