Houdini 16 moves shading and shader building into a new unified context called Material Networks. This masterclass by Kai Stavginski goes over everything you need to use the new context and build custom shaders in it. The result is a Custom Shader with the outputs required for mixing with built-in shaders, where you can blend individual shaders for specific results (displacements, roughness, metallic, etc.). Kai demonstrates the difference between Principled Shader and Principled Shader Core, the Classic Shader and benefit of cached code. Towards the end of the masterclass, Kai also explains OpenGL tags to visualize shaders in the viewport.