5.11 Concluding remarks 147 body [33], biomolecular recognition [35], etc. Recently an image sensor has been demonstrated [33], realized on 1.1 Â 1.3 mm 2 silicon, which has a pixel array of 208 Â 186 pixels. The pixel pitch was 4.6 m m and the size of optical window was about 2 m m. The maximum spectral sensitivity of these m PD was about 640 nm, thus d/ l z 3. 5.11 CONCLUDING REMARKS This chapter reviewed the limits of ubiquitous communication for a nanomorphic cell. Electromag- netic radiation is the primary physical effect used for such ubiquitous communication and this chapter has focused on the basic physics of information transmission via electromagnetic radiation. Estimates were offered for the size/volume and energy required for communication in the nanomorphic cell environment. Discussion in the chapter was devoted primarily to transducers of electrical excitation into electromagnetic waves and vice versa. While there are a number of different components in an EM communication system, it is argued that the size and efficiency of a transducer are the gating factors for nanomorphic cell communications. Therefore, the limiting analyses offered in this chapter center on the electromagnetic transducer (e.g. antenna, LED, etc.) since its scaling directly impacts communi- cation system performance.