I. Introduction  
A. Background and Motivation  
B. Demystifying Human Digital Twin  
C. Related Work  
D. Contributions  

II. A Comprehensive Exploration of HDT  
A. Differences Between HDT and Conventional DT  
B. Traditional Digital Twin in Healthcare is Evolving Toward HDT  
C. The Universal Framework of HDT  
D. HDT: A Hyper-Realistic and Hyper-Intelligent Testbed  
E. Design Requirements and Challenges  
F. Overview of Networking Architecture and Key Supporting Technologies for HDT  

III. Key Technologies for Data Acquisition Layer  
A. Pervasive Sensing  
B. Electronic Health Record  
C. Lessons Learned  

IV. Key Technologies for Communication Layer  
A. On-Body Communication  
B. Beyond-Body Communication  
C. Lessons Learned  

V. Key Technologies for Computation Layer  
A. Multi-Access Edge Computing  
B. Edge-Cloud Collaboration  
C. Lessons Learned  

VI. Key Technologies for Data Management Layer  
A. Data Pre-Processing  
B. Data Storage  
C. Data Security and Privacy  
D. Lessons Learned  

VII. Key Technologies for Data Analysis and Decision Making Layer  
A. Diagnosis  
B. Prescription  
C. Surgery  
D. Rehabilitation  
E. Lessons Learned  

VIII. Future Research Directions  
A. Data Scarcity in HDT  
B. Mobile HDT  
C. Federated HDT in the Cloud/Edge Network  
D. Interoperable Management of Subsystems in HDT  
E. Effective and Efficient Interface Design  
F. Intelligent Blockchain for HDT  
G. Full-Fledged Explainable AI for HDT  
H. Generalized AI for HDT  
I. Green HDT  
J. Metaverse  

IX. Conclusion