Accurate transmission of biological information from within cells and living tissues often requires direct sensing of intracellular states. This review discusses recent advances, challenges, and future perspectives in intracellular sensing technologies and bio-integrated information systems. Embedding sensors or artificial constructs inside cells, rather than relying solely on surface-based approaches, are particularly important for acquiring intracellular biochemical and molecular information. In contrast, certain physical parameters, such as temperature, can in some cases be monitored from the cell surface or extracellular environment. However, intracellular sensing systems face significant challenges, including weak signal output, low signal-to-noise ratios, and limited biocompatibility that restrict their long-term functionality. Addressing these limitations is critical for advancing bio-integrated information technologies.

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