© 2018 The Pharmaceutical Society of Japan. In this review, I tell the story of the cobalt chemistry that has been developed in my group since 2011. First, we achieved the total synthesis of polyketide natural product trichodermatide A, which involved a latestage Isayama-Mukaiyama hydration of an enol ether using cobalt(II) acetylacetonate (Co(acac)2) that gave the desired product chemo-, regio-, and diastereoselectively. After our report of this total synthesis in 2013, we were required to revise the originally reported structure of trichodermatide A following the accurate and important report from the Trauner group. Second, we found unique cobalt-catalyzed hydroelementation reactions of olefins involving a cobalt-salen complex, N-fluoro-2,4,6-trimethylpyridinium salt, and a silane reagent. Under these reaction conditions, a carbocationic or carbon radical species is generated from an olefin, and then C-X (X=O, N, C, F) bond formation occurs with good functional group tolerance for a broad substrate scope. This review also covers recent examples of switching chemistry and natural product synthesis involving my cobalt chemistry reported by several groups.