Waterfall harmonics are a guitar technique where harmonics are played in a cascading or "waterfall-like" fashion, creating a flowing and ethereal sound.

Here's how it's typically done:

1. Natural Harmonics: Start by understanding natural harmonics. These are produced by lightly touching the string at specific points called nodal points, which are typically found at the 5th, 7th, and 12th frets (though other frets can be used for different harmonics). When you pluck the string and touch it lightly at these points, you get a chiming, bell-like sound.

2. Waterfall Effect: Using your right hand, hover your index finger above the desired fret you want to generate a harmonic. Using your thumb, attack the string to achieve the harmonic. Experiment with thumb placement/distance from your index finger! Keep in mind, using nail vs flesh will give you different tones.

3. Technique and Practice: Achieving a smooth and fluid waterfall harmonic effect requires practice and precision. Focus on lightly touching the strings to produce clear harmonics and maintaining a steady picking motion with your thumb as you move across the strings. Keep in mind, your thumb and index finger might not be used to these movements, so give yourself plenty of time to develop this technique.

**Check out Lenny Breau and Ted Green - these two guitar players really pioneered this technique and have made some really special music with it!