This dissertation examines the relationships of established and young startup firms in environments characterized by rapid technological change in which exploration, i.e., moving away from current organizational routines and knowledge bases, is crucial for success. In the first essay, I combine perspectives on organizational myopia and organizational learning to examine how prior successes and prior failures solving R&D problems shape whether established firms go beyond "local search" in partnerships formations with startup firms. In line with the myopia perspective, I find that established firms tend to "overlook" partnering opportunities with novel elements of knowledge as well as opportunities that do not promise payoffs in the immediate future. The study further reveals that prior successes and failures very differently shape these myopic tendencies. While prior failures lead firms to pursue partnerships with novel elements of knowledge, prior successes make firms more receptive to partnerships with payoffs in the distant future. In the second essay, I draw on the literature on organizational learning and inter-organizational partnering to examine the relationship between startup innovation and startup market valuations. I find that startups pursuing innovations that substantially differ from the solutions pursued by established firms may face severe market value penalties as they lack both legitimacy and access to vital complementary assets. This penalty, however, is attenuated if startups commercialize their innovations through partnerships or if they pursue innovations in areas where established firms have failed in their own internal R&D attempts. The final essay draws on the literature on inter-organizational learning to more closely examine the ways in which established firms leverage the knowledge accessed from startup firms. I focus on loosely coupled partnerships that involve established firms paying a research partner for access to specific knowledge. While prior research has questioned the ability of firms to devise new and innovative solutions based on such partnerships, I find that innovation benefits from loosely coupled partnerships do not necessarily stem from the sourcing relationship per se but instead are contingent on the established firm's experimental orientation to pursuing risky projects and its availability of financial and managerial resources. Overall, my dissertation enriches our understanding of the unique interdependencies between established and startup firms in environments characterized by rapid technological change.