When I was younger I used to mess with some really obscure shit called oneirogics. It's obscure enough that I can't even google it.
It's basically substances or methods you can use in order to dream harder. Cholinergic (affecting choline, basically the opposite of anticholinergics which are horrible pesticides ruining everything), and other ways (Maracuya (passionfruit) leaves under the pillow with its distinct smell to remind you you're dreaming when you're asleep, WILD lucid dreaming, etc).
There's like communities around these, and they're the wildest things you'll ever experience. Ever since the dream where I jumped off a train that was taking me to a genocide centre, lived somehow despite this fact, and was stabbed by cosmic nazis by bayonets to death in painstaking detail I've never had anything resembling a nightmare ever since (like a recognizance things aren't happening for real and I can just wake up and laugh) and pretty much stopped that shit because it's super weird and even more underground than the illegal drug scene.
I met a guy in Colombia who was a professor who was studying indigenous people doing this kind of thing, hence the maracuya leaf method. It's like another world, where people deliberately dive into their dreams and come back with insights.
There's an extremely interesting paper to me published in Nature Neuroscience which is the best insight into dreaming I've ever seen, as how it's probably an adaptation for anticipation in a virtual reality kind of environment. When you consider when you see animals like your cat or dog
twitch around when sleeping while lightly barking/meowing it makes total sense [1]
[1] https://www.doaks.org/research/byzantine/scholarly-activitie...