Longitudinally scrutinizing the technological development of laser diodes, this study has examined how highly versatile technologies are developed and accumulated and how they are used in various arenas. The previous chapter showed that the cumulative features of technological development gradually disappeared due to the surge in entrepreneurial spin-outs in the industry in the U.S. Subsequent technological development plays an important role when a technology is still in a nascent stage. Thus, R&D competition in cumulative technological development contributes to technological development until the technology fully matures. According to the technological trajectory perspective, entrepreneurial spin-outs can hinder technological development when the technology is at a nascent stage, because the cumulative effects of incremental innovations on the technological trajectory could disappear if the R&D personnel are thinned out to target different sub-markets. This chapter extends this discussion to two further points: social construction of technological trajectory, and social continuity of technology. First, we consider the dilemma between “thick-trunked technology” and “abundance of fruits,” as well as the strategies that firms can take on this premise. Finally, we discuss the continuity of knowledge in U.S. and Japan.