Recently, the uses of a solar plant factory are being widely recognized in Japan. A solar plant factory may be similar to the computerized greenhouse used in northern Europe (such as in Netherland and Belgium) that has been improved for the past 30 years. This system is quite different from that of the artificial light plant factory, which had been developed by a Japanese company 30 years ago. The solar plant factory is operated using several computers and may be called as a “computer-integrated greenhouse.” One computer may be used for the speaking plant approach on the basis of data processing for physiological and ecological information on horticultural crop cultivation, while the other computers may be used for the intelligent control of the process on a large scale in the greenhouse. For better innovation, scientific discussions and results for such a newly developed area could be introduced in this paper, which had been done according to the technical committees organized by the International Federation of Automatic Control (IFAC) and strongly supported by the Science Council of Japan, a National Member Organization of IFAC.