Ayahuasca, a brew of plants and water, heated to a syrup is known to be one of the most healingest brews on the planet.

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It all starts with a 1-2 meter long stem/vine of a plant rich in a chemical called DMT. Multiple plants are used in the process but, one plant, Banisteriopsis caapi is the most widely used for its quality and composition.  
Every single ingredient is designed to bring out the most intense, days long experience that has changed and continues to change the lives of countless people.
DMT, also known as the spirit molecule, is produced by plants and animals.  In humans, it is produced in the pineal gland near the middle of the head.  Some creatures have more of it than others and it causes the dream state.  Some say it is the root chemical catalyst for consciousness.
The experience is said to be like experiencing time dilation; wherein the user experiences prolonged moments, even lifetimes, in the days of imagination.  
It is also said to be beautifully theraputic, as the body experiences it as well; the people come out changed, almost overwhelmingly for the better.
Retreats are now available for spiritual and religious experiences. 
Here are two incredible testimony videos: