For many of us, dreams are a strange other world -- puzzling, terrifying and beyond our control. But some psychologists now say, under the right conditions, we can control our dreams to have fun or to learn from them.
One way to do that is through lucid dreaming, in which you choose what happens in your dream. You can fly through the air, swim with dolphins, tame the monster in your nightmares, speak to a dead relative -- anything you want to do, all the while aware that it's a dream.
"Lucid dreaming is simply a dream in which you know you're dreaming while it's happening," said Dr. Stephen Laberge, founder of the Lucidity Institute at Stanford University. "So you know, 'This is a dream I'm having,' and therefore, you can control, you can decide. You know it's all in your mind, so nothing can hurt you. You're free and you can experiment."
Recently, people come to the big island of Hawaii for a two-week session with Laberge, who is widely considered to be the country's pre-eminent authority on lucid dreaming.
Stephanie Smedes, an animal eye doctor, is here to learn how to have lucid dreams. One of her goals is to control her nightmares of being chased by an unknown figure, running from room to room.
Smedes hopes that lucid dreaming will "help me to be part of them and then switch them around so I'm not so frightened of them."
At its most basic level, lucid dreaming involves recognizing that you're dreaming while you're dreaming.
"The key to lucid dreaming is [to] remember to do something in your dreams, to notice that it's a dream," Laberge said. "So before bed, you set your mind. Say, 'Tonight, I'm going to be dreaming -- and when I do, I want to remember to notice that I'm dreaming.'"
To train the mind to realize it's in a dream, Laberge sometimes uses a device called "the nova dreamer."
"It's your sleep mask you wear while you're asleep," Laberge explained. "There are sensors on it that pick up the rapid eye movements, where your eyes move when you're dreaming."
The sensor triggers flashing lights that penetrate your consciousness. The lights are a visual cue to become aware that you are dreaming. You can then take over control of your dream as if you were directing a movie.
Two months after the Hawaii conference, ABC News visited Smedes in Seattle to see if she was able to become a lucid dreamer.
"I have had three dreams I would call lucid dreams," she said, "and I've had a number of near successes."
In one especially vivid lucid dream, Smedes found herself flying above the ocean.
"I thought, 'How did you get here? You said you weren't going to fly in your dreams.' And I went, 'Oh, just stop Steph, who cares? Be quiet. Just you're here; be excited,'" she said. "And so I saw, first I saw, one dolphin. And then I saw a school of fish go by. And then I saw a whole pod of dolphins go by. And I got real excited, and I clapped my hands."
Smedes said she hasn't had nightmares again since the Hawaii trip.
But some dream psychologists say lucid dreaming should not be a substitute for dreaming freely.
"The note of caution I would inject is if you focus too much on controlling your dreams, you lose perhaps one of the most valuable aspects of dreams, which is what they're telling you what you don't know about yourself," said Dr. Alan Siegel, author of "Dream Wisdom" and a clinical psychologist at the University of California Berkeley.
But people like Smedes say lucid dreaming has brought them amazing breakthroughs -- claiming they are now the masters of own dreams, for wisdom or just for fun.