1. Introduction  
2. Inferring Affect from FEs  
2.1 Describing Affect  
2.2 An Evolutionist Approach to FE of Affect  
2.3 Applications  
3. A Taxonomy for Recognizing FEs  
3.1 Parameterization of FEs  
3.2 Recognition of FEs  
3.3 FE Datasets  
4. Historical Evolution and Current Trends  
4.1 Historical Evolution  
4.2 Estimating Intensity of Facial Expressions  
4.3 Micro Expressions Analysis  
4.4 AFER for Detecting Non-primary Affective States  
4.5 AFER in Naturalistic Environments  
5. Discussion