Navigating the advertising ecosystem is complicated. Agency holding companies expand and acquire entities at a rapid pace. If you’re targeting agencies, it’s important to know which house they’re under, which brand accounts they’re responsible for, and who the decision-makers are. Here’s a cheat sheet to understand the many agency/brand relationships, how advertisers place their ads, and the technologies they’re using. Winmo’s classic The List® database details all the major holding companies: Omnicom, WPP, Publicis Group, IPG, Havas and Dentsu.