The saying "Form is emptiness, emptiness is form" in the "Heart Sutra" is a famous saying in Buddhism. It means: form (matter) does not exist forever, but is formed by the combination of causes and conditions, so it is essentially Empty; emptiness does not exist eternally, but is formed by the combination of causes and conditions, so it is essentially colored.

This sentence tells us that things have a specific phase in our hearts, and these phases are all recognized by our hearts. The so-called color is emptiness, that is, all external appearances are actually false appearances. Because things are all formed by the combination of causes and conditions. Emptiness is color, which means looking at these external appearances, not being fooled by its changes, but seeing its true face.