A smartphone app for what is hoped to be the world's largest dreaming experiment has been launched at the Edinburgh Science Festival.
DreamON monitors a person 20 minutes before they want to wake, playing a 'soundscape' designed to invoke pleasant scenarios, such as lying by the sea or walking in the countryside.
Participants will then be asked to record their final dream to a database.
Researchers expect up to 10,000 people to take part in the study.
The app has been designed to "manipulate" people's dreams, in an attempt to conjure up situations and experiences inspired by the sounds they are hearing.
It will then sound a gentle alarm to wake the person, who is asked to record their dream to a "dream-catcher" database.
Prof Richard Wiseman, who developed the project, said: "Getting a good night's sleep and having pleasant dreams boosts people's productivity, and is essential for their psychological and physical well being.
"Despite this, we know very little about how to influence dreams. This experiment aims to change that."
Prof Wiseman said it was hoped the app could help people who suffer from depression, who dream more than others, and are more likely to have negative dreams.
He said: "Perhaps improving their dreams might help them."
The Edinburgh International Science Festival runs until 30 April.