Such a great article Thomas and what a great app! We use a lot of Facebook ads for Horsealot (www.horsealot.com), we reached a CPI of 0,26€ for our best ads, but I am currently struggling to reproduce this. After testing so many things, I think that over time the size of my audiences may not be wide enough. How exactly do you segment your audiences? What are your criterias that make you want to seperate an ad set rather than keeping it unique (for each country, sex, age..)? What sizes of audience would you recommend? Thank you so much in advance for your help and congratulations for your work!