This talk is composed of 3 major parts: the iterative creation of a recommender engine, the labeling of images, the post processing of images. After introducing the main topic, labeling images to improve recommendation engine performances, we start with a recommendation engine discussion. We briefly describe the “classical” recommender system (collaborative filtering, content based filtering) and their advantages and limitations. We then describe the re-ranking approach we used to combine different engines into one. Re-ranking is a method (used by Google for example) that takes the different ranking as features and optimizes a certain loss. In our case we combine our different recommendations through a logistic regression that predict the probability of purchases for each tuple (user, sale). This version of the engine led to +7% revenue per customer and is now running in production. We then explain why we wanted to use images information. It seemed that sales with some given images were performing better than others. If we had labels on all images we could use them in a content-based recommender system (used itself in the re-ranking engine). We then described how to label our images using pre-trained models, transfer learning and external APIs. We also show how easy it is to steal these APIs. The final part deals with post processing of the images. Since most pre-trained models only output one class prediction, we need to reshape these into broad themes that can be used in our engine. We use a Non Negative Matrix Factorization for this purpose and show that we have very interpretable results. We conclude by comparing visually the different engines. The key take away (more information in the pitch part) are theses: - Machine learning: overview of recommender systems, re-ranking, how to label images, transfer learning. - Do iterative data science. Start simple, then try more complex systems. - Avoid rushing in deep learning without checking what you can find on Internet. Use pre-trained models and transfer learning. There is a lot of hype around deep learning and image recognition. However, there are not that many success stories for web pure player companies. In our case we explain how we started with simple recommender systems before improving them gradually and finally using images information. One of the key take away is the following: do iterative data science. Always prefer shipping a minimum viable product before creating something complex. At our clients, we commonly see teams rushing into images projects for the only purpose of doing deep learning without a clear ROI in mind. We insist on the fact that deep learning is not an end in itself. Here, it boils down to making new information available in the system. In this sense, deep learning methods are just an extension of Business Intelligence.