Part of the goal [of this issue of the Experimental Political Scientist, the official newsletter of the American Political Science Association Organized Section on Experimental Political Science,] is to serve as a catalog of ideas for experiments, jumping-off points to which students can add their own spin. The contributions herein fall into two broad categories:

1. The mechanisms of how to conduct the experiment. A lot of tacit, on-the-ground knowledge is required to successfully implement an experiment. Rather than simply something to be "checked off" as valid in service of a specific quantitative finding, we're interested in highlighting the often innovative and complex work that goes into constructing what Morton (2013) calls the "methods and materials" of an experimental protocol.

2. Unexpected events. It is a shame to think of an ideal experiment as one in which the experimenters are able to perfectly predict what will happen.

While it's important that the core mechanisms of interest operate correctly, we want to highlight serendipity as a way to inform both future experimental design (when you learn how you *wish* you had implemented the experiment) or theoretical progress (when something unexpected happens that makes you think of other interesting things to test).

We have six excellent contributions on this theme. The topics range from best practices to running experiments with online livestreams or how to design treatments for experiments using recommendation algorithms, to lessons learned from conducting field experiments with excombatants. Thanks to the authors of these six contributions:
 

• Lynn Vavrek
• Vin Arceneaux
• Neil Malhotra
• Mateo Vasquez-Cortes and María Ignacia Curiel
• Kirill Chmel, Eunji Kim and John Marshall
• Chloe Ahn, Drew Dimmery, Sangyeon Kim, and Kevin Munger