In the quest for longevity and immortality, Chinese, like other ancient civilizations such as Egypt, Arab, Greece, and the Middle Age Europe, had embarked on the journey of Alchemy, which in dictionary is defined as the methods for transmuting baser metals into gold and with finding a universal solvent and an elixir of life.
In Daoist tradition, there are two types of Alchemy, namely External Alchemy (外丹) and Internal Alchemy (内丹). External Alchemy refers to the cooking and fusion of external metal and chemicals to produce medicine for immortality, and Internal Alchemy refers to the cultivation and transformation of internal essence-energy-spirit (three treasures) to achieve longevity and immortality.
The external alchemy, like the many attempts in other countries throughout history, had not been successful in terms of achieving longevity and immortality, and in many cases had led to the killing of people due to metal/chemical poisoning. Internal alchemy, on the other hand, had aid countless people achieve health and longevity, as reported by Daoist Internal Alchemy masters such as Wei BoYan 魏伯阳(~151A.D.-?), LuDongBin 吕洞宾 (796A.D-?), ZhangBoDuan 张伯端 (983-1082A.D.), LiDaoChun 李道纯(1277-1305A.D.) and ZhangSanFeng 张三丰(1247-1458A.D.).
Internal Alchemy: 5 stages
Over the years Daoist had classified Internal Alchemy into 5 Stages: Building Foundation (筑基), Transform Essence into Energy (炼精化气), Transform Energy into Spirit (炼气化神), Transform Spirit back to Nothingness (炼神还虚), and Transcend Nothingness in accordance to Dao (炼虚合道). Building Foundation refers to the acquiring and understanding of the essential knowledge about one self and reality, and to the basic healing of the body and the mind. Transform Essence, Energy, and Spirit refer to the owning, mastering, and transcending of body, mind, and consciousness respectively. Transcend nothingness refers to transcending of all attachment/aversion/identification and live in accordance to Dao.
Internal Alchemy: 4 Approaches
To cater for the diversity of background and stage of spiritual development, countless Internal Alchemy methods had been invented over the history to suit people with different needs. LiDaoChun (李道纯), master of QuanZhen Middle Branch (全真中派) in the 13th Century, had classified various Daoist practices into 9 side tracks and 4 main approaches. The 4 main approaches consist of the Lower, Middle, Upper and Highest Approach.
Lower approach (下乘) focuses on the alchemy of physical body, which when couple with sentiment transcendence could nurture life. The middle approach (中乘) focuses on the alchemy of energy body, which when practice ceaselessly could extend life. The upper approach (上乘) focuses on alchemy of body and mind, which represents a high road to longevity, and when practice single-heartedly could lead to immortality. The highest approach (最上一乘) focuses on the alchemy of mind, consciousness and nothingness, which is the pathway for Outmost person, and leads to Dao realization. (Source: Li Daochun, Zhongheji/Book of Balance and Harmony, Chapter 2. 李道纯, 中和集, 卷二)
在追求长寿和长生不死，中国，跟其他古代文明，如埃及，阿拉伯，希腊和中世纪的欧洲等，都有炼丹/炼金术的记载。炼丹/炼金的字典解释为: 将劣等金属转变为金子，或者是将不同物质转变为长生不老药。
在道家的传统中，有两种类型的炼丹术: 即外部炼金术的外丹，和内丹。外丹是指烹饪和融合外部金属和化学品以生产医药，内丹是指人培养和转化内在的精 – 气 – 神（三宝）来实现长寿和长生。
外丹的研炼，像其他国家的许多尝试，都不甚成功，并且在许多情况下，引致很多人由于金属/化学品中毒而死亡。内丹，另一方面，则帮助了无数人实现健康和长寿，道家在历史上就有很多有成就的内丹大师，如魏伯阳（151A.D. – ？），吕洞宾（796A.D-？），张伯端（983-1082A.D.），李道纯（1277-1305A.D.）和张三丰（1247-1458A.D.）等。
内丹：五个阶段
多年来道家划分内丹为五个阶段：筑基，炼精化气，炼气化神，炼神还虚，炼虚合道。筑基指的获取和了解自我和道的基本知识，以及基本身体和精神的健康。炼精化气，炼气化神，炼神还虚是指承担，掌握和超越的身，心，和意识。炼虚合道是指超越所有执着/厌恶/识别而成道行道。
内丹：四乘方法
为了满足不同背景和发展需要，历史上发明了有很多不同的内丹方法，以满足人们的不同需求。 李道纯，全真教中派老师，在十三世纪就将道家所有丹法分类为旁门九品，和四乘丹法，包括下，中，上渐法三乘，和最上一乘。
下乘专注于身体的修炼，如配合调心能养生。 中乘专注于气的锻炼，能延长寿命。上乘专注于身心相修，是一条长寿之路，实践全心全意时，能长生不死。最上一乘专注于心，意和虚无，这是至人的途径，导致道的实现。 （来源：李道纯，中和集，卷二）