Deep reinforcement learning has shown remarkable success in the past few years. Highly complex sequential decision making problems from game playing and robotics have been solved with deep model-free methods. Unfortunately, the sample complexity of model-free methods is often high. Model-based reinforcement learning, in contrast, can reduce the number of environment samples, by learning an explicit internal model of the environment dynamics. However, achieving good model accuracy in high dimensional problems is challenging. In recent years, a diverse landscape of model-based methods has been introduced to improve model accuracy, using methods such as probabilistic inference, model-predictive control, latent models, and end-to-end learning and planning. Some of these methods succeed in achieving high accuracy at low sample complexity in typical benchmark applications. In this paper, we survey these methods; we explain how they work and what their strengths and weaknesses are. We conclude with a research agenda for future work to make the methods more robust and applicable to a wider range of applications.