Today Is...World Dream Day

Scientists are not totally sure what they are but Descartes based his whole 'I think, therefore I am' philosophy on one of his, Einstein developed his theory of relativity after one about cows, the Sewing Machine was invented because of one and H.P. Lovecraft used his to write his horror books
as did Mary Shelley so we may not know what they are or why we have them, but they can be some very handy function of your brain's pineal gland activity.
I did find out that puffing too much on my ecigarette before being tucked up for the night can create some very lucid dreams which is cheaper than the dream scientists electromagnetic instruments to excite your hormones which they use to induce lucid dreams in experiments.
As well as frying your brain with magnetic waves, they also found that smells introduced into your sleeping nostrils cause dreams and the worse the smell the more negative the dreams as our sense of smell has a direct line to the subconscious areas of the brain, which affects emotion, mood, and memory so if wake up in a cold sweat after being chocked to death by the vacuum cleaner, check if your partner laying next to you had beans for their tea because they could be responsible for causing the nightmares.  

Experts say that every night we on average experience around five dreams and they think they reflect our current state of mind and have interpreted the meanings of the most common dreams:

Teeth falling out (anxieties about your appearance and how others perceive you)
Being chased (you have issues that need to be tackled)
Unable to find a toilet (having trouble expressing yourself)
Being naked (you feel wrongly accused or exposed by someone)
Failing exams (you are in a situation you don't feel confident about)
Flying (someone or something is stopping you from moving to the next step in your life)
Falling (signifies insecurity and anxiety about a situation)
Crashing a car (You are unsure of the direction you are taking)
Running late (You feel like you are running out of time to get something done)
Wild Animals (You feel oppressed or constricted)
Ghosts (overwhelmed to guilt or the fear of something)
Dying (Concerns over a significant life change such as a breakup, leaving a job or relocating)