1. Introduction

2. The Econometrics Panel Data Literature

3. Setup and Data Configurations

4. Potential Outcomes, General Assumptions, and Estimands

5. Two-Way-Fixed-Effect and Difference-In-Differences Estimators

6. The Staggered Adoption Case

7. Moving Away from the Two-Way Fixed Effect Structure

8. Nonlinear Models

9. Design-based Approaches to Estimation and Inference

10. Open Questions for Further Research

11. Recommendations for Empirical Practice