Another product review: Peter Coppola's DNA (Hydrating Hair Serum - soy-based):
I bought this stuff randomly and LOVE it! It's very hydrating without making hair oily. The directions say to add a few drops to your normal leave-in hair product or you can apply it directly to hair. I just add it to my night-time hair repair stuff and it seems to really help. It doesn't smooth your hair cuticle, but it does hydrate.