Omnicom Group Inc. encompasses several media divisions, with the primary one being Omnicom Media Group (OMG). OMG includes notable agencies such as OMD, PHD, and Hearts & Science. These agencies specialize in media planning and buying, data analytics, and audience engagement across various platforms. For more detailed insights into their operations and services, you can visit the official Omnicom website or explore specific agency sites under the Omnicom umbrella.