In dream state
I found that in dream state we are so relaxed that we can get visitations from our loved ones. Sometimes it happens when a loved one has just passed or later when they come to share a message and it is real. We live with our five senses and when we are awake our mind will question these dreams and we may tell ourselves that is was only a dream.
Spirit dream visits are so real that they are totally different from other dreams. They seem to be much brighter and also they may come to pass on a message or for Spirit to say they are a part of our life and that they love us still.
I know that when we are asleep our five senses, mixed with our super-sense freedom of the super consciousness, give us a level where we interact with loved ones. We raise our frequency and Spirit lowers theirs to meet us on the astral plane.
We have to go back to our roots to understand why we need to dream and also there are the spiritual aspects of this most interesting subject.

History of dreams
This what l have gleaned from research the world web various sources
“There are documented in clay tablets dream interpretations that go back as far as 3000-4000 BC. In primal tribes they were unable to know which was dream world or what was reality was. They saw that the dream world is an extended part of reality and is very powerful.
Greeks and Romans who went into battle would have dream interpreters accompanying the military leaders. They thought these dreams were indeed a message from the gods be seen in religious themes. Egypt is famous for dream interpreters as they recorded their dreams in hieroglyphics. People who had the ability to decode dreams were blessed and thought to be special. They were looked up to and seen to be divinely gifted.
We can see that the dreams were prophetic. It was an oracle or omen from outside spirits, whether it was a message from a deity, from the dead or even the works of a demon. Dreams often aided in diagnosis for the medicine men. Dreams were a vital clue for healers in deciding what was wrong with their patient and they were used to make a diagnosis. People in ancient Greece and ancient China looked to their dreams for their next course of action.
Dreams can be seen as an actual place that your spirit and soul leaves every night to visit. The Chinese believed that the soul leaves the body to go into this world. However, if they should be suddenly awakened, their soul may fail to return to the body. For this reason, some Chinese today are wary of alarm clocks. Some Native American tribes and Mexican civilisations share this same notion of a distinct dream dimension. They believed that their ancestors lived in their dreams and take on non-human forms like plants. They see dreams as a way of visiting and having contact with their ancestors. Dreams also helped to point to their mission or role in life. The term ‘dream-time�as it relates to the Aboriginal religion and belief system, all life, including humans, animals and plants are a part of an organised network which can be traced back to the original spirits of dream-time. The dream-time dictates the spiritual, religious, and social aspects of almost all Aboriginal culture, directly reflecting these people's beliefs, values, and ideas.
The tie to dream-time is so strong and unique in the everyday lives of the tribes that the creation of earth is enacted during rituals of dance and celebration. As the name may suggest, dream-time is practiced personally through revelations, visions and the actual dreams of each Aborigine and these personal religious practices are what explain the meaning of life and answer the question of why they are on this earth."