With investors spending billions of dollars in recent years, yesterday's billboards have been replaced by highly targeted ads delivered over the Internet. We talked to three ad-tech entrepreneurs at Metamorphic Ventures, a venture capital fund that runs an incubator in New York. Vivek Sharma's company, Movable Ink, allows advertisers to send emails with content that will change, based on when the consumer opens the email, or where the person is shopping. Erik Matlick is the CEO of Madison Logic, which has created a technology that sits on publishers' websites, collects data and allows big advertisers to reach their target market. 33Across also collects data from publishers that co-founder Eric Wheeler uses to help consumer brands reach their ideal customers, such as new parents.