Which organ is part of the Yin category?

The heart is considered part of the Yin category due to its associations within Traditional Chinese Medicine (TCM). In TCM, organs are classified into Yin and Yang categories based on their characteristics and functions. Yin organs, also known as solid organs, are responsible for storing and maintaining essential life substances, such as blood and essence.

The heart plays a crucial role in this framework as it governs blood circulation and houses the "Shen" or spirit, which is essential for emotional and mental well-being. It is characterized by qualities such as fullness, stability, and substance, aligning it with the Yin properties.

In contrast, the other organs listed—such as the gallbladder, large intestine, and san jiao—are categorized as Yang organs, which generally have more active and dynamic roles in processes like digestion and metabolism. Yang organs often have hollow structures and are involved in the movement and transformation of materials rather than storage. This distinction underscores why the heart is uniquely identified with the Yin category, highlighting its role in maintaining balance and harmony in the body's functions.