This document summarizes research on emotion recognition using convolutional neural networks (CNNs). It surveys various CNN-based facial expression recognition systems proposed by different researchers. The document examines how CNNs can be used for facial expression recognition (FER) and compares CNN-based techniques to traditional machine learning approaches. It also analyzes the CNN architectures and datasets used in previous FER studies. The document concludes that smaller CNN models with fewer layers are suitable for full frontal face images, while more complex images require deeper CNNs with greater numbers of layers and parameters.