Due to the broadband solar spectrum, the energy conversion efficiency is bounded to be less than 31% in current single-junction solar cells, known as the Shockley-Queisser (SQ) limit. One of the essential assumptions in reaching this SQ limit is that the semiconductors can at most create one electron-hole pair (i.e., an exciton) after absorbing one photon with energy above the bandgap. Singlet fission in certain organic semiconductors can potentially circumvent this limit by splitting one photo-excited singlet exciton into two triplet excitons. Nonetheless, the mechanism of singlet fission is not transparent with intensive debate on whether a direct coherent coupling scheme or an indirect charge-transfer picture is the primary origin. In this talk, I’ll briefly summarize the latest progresses in the field, show our recent experimental evidences for a coherent coupling scheme involving delocalized excitons in a protypical system of crystalline tetracene, and propose potential applications of singlet fission beyond solar conversion.