Acharya Prashant explains the process of moving from the gross to the subtle by using the analogy of pestling a heart in a mortar. He describes how the gross mind is attached to material forms and crystals, but through the process of grinding or 'pestling', these patterns are broken down into fine powder. This reduction in size represents the destruction of form, shape, and color, leading to the realization that everything shares the same essence. He points out that even solid matter, when probed deeply at the atomic and molecular levels, is revealed to be mostly empty space and eventually nothingness, proving that material attachments are based on a false perception of solidity.