If Qi is the most famous concept in Traditional Chinese Medicine, it's actually one-third of an older, foundational trio known as the Three Treasures (San Bao): Jing, Qi, and Shen. Together, they're traditionally described as the three layers of substance and energy that make up a living person — from the most physical and dense, to the most subtle and refined.
Jing: Essence
Jing is usually translated as "Essence," and it's the densest, most material of the three. It's inherited from one's parents at conception (Pre-Heaven Jing) and is considered finite — a kind of constitutional reserve gradually spent over a lifetime. It can be supplemented somewhat through diet, rest, and lifestyle (Post-Heaven Jing, drawn from food and water), but classical theory treats it as fundamentally non-renewable in the way Qi is.
Jing is associated with growth, development, reproduction, and the aging process itself. Traditional descriptions of Jing depletion sound a great deal like descriptions of aging: weakening bones and teeth, graying hair, reduced fertility, and declining vitality. A great deal of TCM longevity practice is explicitly about conserving Jing rather than spending it carelessly.
Qi: Vital Energy
Qi sits above Jing in subtlety — it's the dynamic, moving energy that animates the body, often translated as "vital force." Where Jing is the substance, Qi is closer to the activity — it's what allows Jing to be transformed, moved, and used. Qi powers digestion, circulation, and the immune response, and is renewed daily through breath and food, unlike the more finite Jing.
Shen: Spirit
Shen is the most refined of the three, often translated as "Spirit" or "Mind," and is associated with consciousness, mental clarity, emotional presence, and a sense of being fully "there." Classical texts describe Shen as housed primarily in the Heart, and a person with abundant, settled Shen is traditionally described as having clear eyes, a calm presence, and quick, lucid thinking.
Why they're treated as inseparable
The Three Treasures aren't really three separate things stacked on top of each other — they're traditionally described as mutually dependent, transforming into one another. Jing is the root from which Qi arises; Qi, refined further, nourishes and stabilizes Shen. Weakness in one layer is thought to eventually affect the others: severe, prolonged Qi deficiency can eventually deplete Jing; profound Shen disturbance can scatter Qi.
This is part of why a TCM assessment so rarely separates "physical" from "mental" health — in this framework, they were never really separate to begin with. The Three Treasures offer a useful vocabulary for something most people intuitively recognize: that constitution, energy, and state of mind are different expressions of the same underlying vitality.