1 Introduction  
1.1 Structure of the article  
2 Theoretical Background  
3 The Vanilla VAE and Its Problems  
3.1 The Balancing Issue  
3.2 Variable Collapse Phenomenon  
3.3 Aggregate Posterior vs. Expected Prior Mismatch  
3.4 Blurriness  
3.5 Disentanglement  
4 Two-Stage VAE  
5 Regularized VAE (RAE)  
6 Hierarchical Variational Autoencoder  
7 Experimental Setting  
7.1 Green AI and FLOPS  
7.2 Fréchet Inception Distance  
7.3 Architectures Overview  
8 Numerical Results  
8.2 Energetic Evaluation  
9 Conclusions