Chromosome territories (CTs) are a fundamental feature of nuclear architecture, and their study has significant implications for understanding epigenomics. The concept of CTs was first introduced by Theodor Boveri in the early 20th century, who observed that each chromosome in interphase retains its individuality and occupies a distinct part of the nuclear space. Early evidence for CTs was provided by microscopic studies, but the concept fell into disuse due to electron microscopic evidence suggesting that chromosomes were unravelled into chromatin fibers. However, recent advances in techniques such as laser microirradiation and in situ hybridization have reaffirmed the existence of CTs. CTs exhibit nonrandom arrangements, with gene density correlated radial distributions, and proximity patterns that reflect functional interactions. These arrangements are stable during interphase but can change during cell cycle events and postmitotic differentiation. The structure and dynamics of CTs, including their shapes, plasticity, and interactions, are still under investigation. Techniques like 3D FISH and chromosome conformation capture (3C) have provided insights into the spatial interactions within and between CTs. The CT-IC model proposes that nuclei are composed of CTs and the interchromatin compartment (IC), which contains splicing speckles and nuclear bodies. The IC is a DNA-free space that may facilitate transcription and RNA splicing. Other models, such as the "lattice" model, suggest a network of chromatin fibers, but the CT-IC model remains the most widely accepted framework. Despite these advancements, many questions remain about the functional implications of CT arrangements and the mechanisms underlying their formation. Future research will likely focus on understanding the dynamic behavior of CTs during cellular processes and the role of specific gene loci within and between CTs.Chromosome territories (CTs) are a fundamental feature of nuclear architecture, and their study has significant implications for understanding epigenomics. The concept of CTs was first introduced by Theodor Boveri in the early 20th century, who observed that each chromosome in interphase retains its individuality and occupies a distinct part of the nuclear space. Early evidence for CTs was provided by microscopic studies, but the concept fell into disuse due to electron microscopic evidence suggesting that chromosomes were unravelled into chromatin fibers. However, recent advances in techniques such as laser microirradiation and in situ hybridization have reaffirmed the existence of CTs. CTs exhibit nonrandom arrangements, with gene density correlated radial distributions, and proximity patterns that reflect functional interactions. These arrangements are stable during interphase but can change during cell cycle events and postmitotic differentiation. The structure and dynamics of CTs, including their shapes, plasticity, and interactions, are still under investigation. Techniques like 3D FISH and chromosome conformation capture (3C) have provided insights into the spatial interactions within and between CTs. The CT-IC model proposes that nuclei are composed of CTs and the interchromatin compartment (IC), which contains splicing speckles and nuclear bodies. The IC is a DNA-free space that may facilitate transcription and RNA splicing. Other models, such as the "lattice" model, suggest a network of chromatin fibers, but the CT-IC model remains the most widely accepted framework. Despite these advancements, many questions remain about the functional implications of CT arrangements and the mechanisms underlying their formation. Future research will likely focus on understanding the dynamic behavior of CTs during cellular processes and the role of specific gene loci within and between CTs.