Simplify the following text for a Grade 7 native English-speaking person.
Original: The first book to recognize the scientific potential of lucid dreams was Celia Green 's 1968 study Lucid Dreams .
Simplified: Although some people can have lucid dreams without trying , most people do not have them often . It is important to be able to remember dreams , because if the dreamer does not remember them , he or she will not know if they were lucid dreams or not .