I already had such experiences...this is very intriguing and I suppose this is due to altered state of conscience while the sleep and a little play with "what is real ?" and "what is at least what you think is reality"...This is always very interesting to me when I have such dream into dream because it helps me remember there is not just one reality but a lot of frequencies I can choose to be turned on...

There is another thing I often experience while dreaming and that is suddenly remembering that I naturally fly, not like a bird but in a standing position, I can just jump and fly and I feel intensely that it is my normal state and I had just forgot it...this is what I enjoy most at the moment : remembering, as if I was finally awake and no more in a sleeping-forgetting state of my own super powers ;-) Weird but wonderful feeling 😉
And I do not take any substance, I swear 😄