 Autoencoders are often trained with only a single layer encoder and a single layer decoder, but using deep encoders and decoders offers many advantages.Geoffrey Hinton developed a pretraining technique for training many-layered deep autoencoders.This method involves treating each neighbouring set of two layers as a restricted Boltzmann machine so that the pretraining approximates a good solution, then using a backpropagation technique to fine-tune the results.