You're going to use your understanding of Pandas series during a critical part of the machine learning design process that's feature engineering. When you're developing a machine learning model, you'll often find that you can boost the performance of your model by creating new variables or features. For example, you might want to, in this case, multiply the length and the width features to create a new area feature for your dataset. So after creating this LW data frame with length and width values, I'm coming down here and I'm creating a new series called area. And the way that I set that is by multiplying the length series, by the width series, and then when I execute that cell, it creates this new area series. In essence, that's what you're going to be doing in the feature engineering process of machine learning.