To transmit information from within cells or living tissues, sensors or artificial objects must be embedded inside cells or tissues, rather than on the surface of the tissue, to accurately extract the internal information. However, sensors and artificial objects embedded in living tissues or cells emit weak signals, have low signal-to-noise ratios, and lack biocompatibility to withstand long-term use. This special issue highlights the fundamental research and related technologies aimed at solving these challenges, as well as emerging trends toward future biological information transmission. It introduces technologies that contribute to building systems capable of sustaining the long-term functionality of artificial sensors embedded in living tissues and cells, thus paving the way for a society in which these systems can be realized.