1. Introduction  
2. Multi-Omics Data  
2.1. Traditional Molecular Omics Data  
2.2. Non-Molecular Omics Data  
3. Challenges in Multi-Omics Data Analysis  
3.1. The Curse of Dimensionality  
3.2. Imbalance Problem  
3.3. Missing Value  
3.4. Heterogeneity  
3.5. Noisiness  
4. Multi-Omics Fusion Strategies  
4.1. Feature-Level Fusion  
4.2. Decision-Level Fusion  
5. Open-Source Software  
6. Multi-Omics Datasets  
6.1. Datasets Description  
6.2. Online Portals/Platforms  
7. Discussion and Future Directions  
8. Conclusion