Researchers claim that lucid dreaming, in which the dreamer has full control over his dreams, is possible.

The researchers found that applying a weak alternating electric current at a frequency of 40 hertz to the frontal and temporal brain regions, where high-frequency 'gamma' brainwaves had previously been associated with lucid dreaming, after three minutes of uninterrupted Rapid Eye Movement (REM) sleep led to volunteers waking up and stating that they had lucid dreams.
The researchers said that their findings could be helpful in treating patients suffering from post traumatic stress disorder, who are often plagued by nightmares. “Promoting gamma oscillations during REM sleep in post-traumatic stress disorder with re-emerging nightmares might trigger lucid dreaming and eventually enable active changes in dream content”, the researchers wrote in their report.
Source-Medindia