The North Star Metric (NSM) is a quantitative measure used to track the success and growth of a product. For Reels, the NSM could be the number of users who watch at least one Reel per day. This metric would help the Reels team understand how engaging their content is and how many people are using the feature on a daily basis. However, it's important to keep in mind that focusing solely on the NSM can have trade-offs. For example, if Reels went up but Newsfeed Posts went down, it could mean that users are shifting their attention away from the newsfeed and towards Reels. This could be a positive outcome for the Reels team, but it may have negative implications for the overall user experience on the platform. As a product manager, it's important to consider the trade-offs associated with any metric or feature and make decisions that prioritize the long-term success and satisfaction of the user base. This may involve adjusting the NSM or implementing changes that balance the competing needs of different features. Ultimately, the goal is to create a cohesive, engaging, and user-friendly product that meets the needs and expectations of the target audience.