Fully homomorphic encryption (FHE) is an encryption scheme that allows arbitrary computations on encrypted data without decrypting it. Since its concept was firstly introduced by Rivest, Adleman and Dertouzos in 1978, there had been many trials to realize a secure FHE scheme due to its attractive applications, but all were failed for 30 years. In 2009, Gentry finally succeeded in designing a secure FHE scheme by introducing a new design strategy and providing an instantiation from ideal lattices. Following Gentry's blueprint, there have been proposed various FHE schemes to improve efficiency. In this talk, I will present Gentry's technique to construct FHE schemes with examples and introduce basic applications of FHE schemes.