Since Hashirama Senju's death, the Sharingan or Wood Release had become indispensable for subduing the Tailed Beasts. Thus, Konoha began devoting the entire village's resources to researching how to recreate the First's secret Wood Release techniques. However, Hashirama Cell transplant experiments conducted on adult volunteers failed completely, claiming many lives. The attempt was consequently classified as a forbidden technique and sealed away. Yet, in order to collect all kinds of ninjutsu, Orochimaru continued the banned Hashirama Cell transplant experiments. He successively abducted genin, chunin, Anbu members, and sixty infants from villages around Konoha. He extracted genetic material from the First's corpse and injected it into the bodies of the sixty infants for human experimentation, but the rejection reactions were severe, and they died one after another...
After the First Hashirama Senju died, Konoha had launched an experimental program involving Hashirama Cell transplants in hopes of producing Wood Release ninja once more. It was later prohibited by the Third Hiruzen Sarutobi because there were too many casualties and no results. However, Shimura Danzō later secretly restarted the Hashirama Cell transplant project. Orochimaru helped Danzō carry it out, and it produced results—Yamato, who could use Wood Release, was born this way. At the time, however, Orochimaru himself did not know that one of the sixty infant test subjects, Yamato, had survived and inherited Wood Release. Otherwise, this forbidden experiment could not possibly have produced only Yamato as a result. As the years passed, Orochimaru was astonished to discover that one infant test subject had survived—and that infant was the future Yamato.
Another experimental technology Orochimaru had mastered was perfect cloning. However, Orochimaru did not seem particularly fond of the forbidden practice of cloning. The main reason he cloned so many Shins was that Shin's constitution was highly unusual: transplanting any organ into