1 Introduction  
2 The Data Distillation Framework  
2.1 Data Distillation by Meta-model Matching  
2.2 Data Distillation by Gradient Matching  
2.3 Data Distillation by Trajectory Matching  
2.4 Data Distillation by Distribution Matching  
2.5 Data Distillation by Factorization  
3 Data Modalities  
4 Applications  
5 Challenges & Future Directions