A BSTRACT  
1 Introduction  
2 Data Caching Review  
2.1 Layer 1 Caching  
2.2 Layer 2 Caching  
3 Deep Learning Outline  
3.1 Feed forward Neural Network (FNN)  
3.2 Convolutional Neural Network (CNN)  
3.3 Recurrent Neural Network (RNN)  
3.4 Auto Encoder  
3.5 Deep Reinforcement Learning (DRL)  
4 Deep Learning for Data Caching  
4.1 FNN and CNN  
4.2 RNN  
4.3 Auto Encoder  
4.4 DRL  
5 Research Challenges and Future Directions  
5.1 Caching as a Virtual Network Function Chain  
5.2 Caching for Mobile Augmented Reality (MAR) applications and Digital Twins (DTs)  
5.3 Deep Learning for Cache Dimensioning  
5.4 The Cost of Deep Learning  
6 Conclusions