This is one of the cool secrets. If you want to correct light leakage or light artifacts, or you want to have more control over light and shadow, or you want
Emission — Blender Manual
Create a perfect circular and elliptical motion without curves
Blender Lighting Compositing For Beginners, Blender Emission Map
light - Eevee emission reflections disappear when out of view - Blender Stack Exchange
What is the Emission node in Blender 3D, and how is it used? - Quora
Blender Supports Negative Light - Blender Tests - Blender Artists Community
Tutorial: Cycles Volume Scatter Explained
Awesome Creative Videos
Negative light and emission in Blender
light - How can I have a strong emission object without it turning white? - Blender Stack Exchange
ACV MUSIC 1
Lights with Negative Values in Blender
rendering - Table Lamp effect gone really bad on Eevee - Blender Stack Exchange