The nucleus, serving as a pivotal regulatory and control hub within the cell, governs numerous aspects of cellular functions, including DNA replication, transcription, RNA processing and so on. Therefore, any deviations in nuclear morphology, structure or organization can profoundly impact cellular activities. In this review, we provide an updated perspective on the structure and function of nuclear components, with a specific focus on the linker of nucleoskeleton and cytoskeleton complex, the nuclear envelope, the nuclear lamina and chromatin. It is crucial to note that nuclear size should not be overlooked but rather considered as a fundamental parameter for cellular state. Its regulation is tightly linked to environmental changes, development and various diseases, including cancer. Hence, we also provide a concise overview of different mechanisms by which nuclear size is determined, the emerging role of the nucleus as a mechanical sensor, and the implications of altered nuclear morphology on the physiology of diseased cells.