The article explores new ways to model international trade in economic models. It introduces theories that consider how different types of firms interact in global markets. By using these advanced theories, the researchers show that the structure of firms in a model can affect outcomes like economic integration and climate policy. They find that including a diverse range of firms can lead to more variety in products and better productivity. Additionally, when looking at climate policies, the model shows that certain trade patterns can worsen carbon emissions issues. Overall, the study highlights the importance of considering different types of firms in economic analysis.