Fans of Bill Nye, Topher Grace and the seminal podcast “Serial” can rejoice — there’s new audio content coming to your earbuds soon. Seven major podcasts networks such as NPR, Stitcher, Wondery, ESPN and IHeartPodcast Network — as well as independent outfits like “Serial” and “Armchair Expert” — unveiled their upcoming lineups and partnerships at this month’s Winter Podcast Upfront in Beverly Hills. In total, the podcast networks gave advertisers and media a glimpse of how big podcasts have become, growing into an industry that has daily podcast downloads in the tens of millions, according to researchers. Here are some of the highlights from the event: 1. Podcast listenership is still niche, but on the rise The share of the U.S. population listening to podcasts has doubled in the last four years, increasing from 1.7 percent in 2014 to 3.9 percent in 2018, according to Tom Webster, SVP of the podcast research company Edison Research, which has partnered with networks like PodcastOne and NPR for private research and consulting. While this is still a smaller percentage compared to how much we listen to AM/FM radio (45 percent in 2018), Webster estimates that tens of millions of hours of podcasts are being downloaded daily across all platforms. The full study, called Share of Ear, will be released on March 6. 2. Dax Shephard hits 1 million listeners per podcast After debuting last February, the interview podcast “Armchair Expert With Dax Shepard” grew to become the most downloaded new shows of the year, according to Apple iTunes. At the upfront, Public Media Marketing unveiled that the podcast has reached an average of 1 million podcast downloads per episode. “We’ve never seen a show grow so quickly,” CEO of podcast marketing company Public Media Marketing David Raphael, who also works with the highly successful “The Joe Rogan Experience,” told TheWrap. “Serial had ‘This American Life’ to launch from. Dax didn’t. There was no reason other than the fact that the show is connecting.” “Armchair Expert” joins fellow independent podcasts like “Your Mom’s House With Tom Segura and Christina Pazsitzky” and “The Joe Rogen Experience” as podcasts that have crossed the threshold of a million downloads per episode on average, Raphael said. 3. “Serial” is back to hit the books As previously reported by TheWrap, the investigative podcast series “Serial” — which helped popularize the genre with a true-crime first season that inspired an upcoming HBO docu-series, “The Case Against Adnan Syed” — announced that its next project will take a deep dive into the U.S. public school system. The still-untitled series will track the history of a single public school through a century of sweeping social changes and major educational reforms. Through personal stories and plot twists, it will examine how the school reflects an ultimately failed effort to create equality in America. It’s set for release during the fourth quarter of 2019. The new project, to be hosted by Peabody Award winner Chana Joffe-Walt and produced by “Serial” co-creators Sarah Koenig and Julie Snyder, will be a limited series rather than the official fourth season of “Serial.” 4. Expect more ads in your favorite podcast Like many popular podcasts, “Serial” is taking a different approach to advertising with content partnerships with brands that feel integrated into the program. For “Serial” season 3 last year, PMM partnered with job search website ZipRecruiter for a series of ad spots called “Road to Hired,” focused on an individual who used the site to advance their careers. The goal was to have ads feel fully integrated into the storytelling style of “Serial.” Raphael noted that Vital Farms saw a 96 percent brand lift after the campaign it did with PMM podcasts. Hotel booking website HotelTonight is also praising its partnerships with podcasts. During ESPN’s presentation of its podcast arm ESPNAudio, ESPN commentator Stephen A. Smith presented a statement from the senior manager of acquisition marketing at HotelTonight David Gee, citing “a whopping 288 percent increase in awareness” after its first campaign with ESPN podcasts. 5. Bill Nye and more stars come to podcasts Stitcher’s upcoming lineup will include the Science Guy himself: Bill Nye. The famed science commentator will host “Science Rules!” where he will take listener calls with co-host Corey Powell, using field experts and special celebrity guests to “answer the curliest science questions,” Stitcher said in a statement. “Science Rules!” will launch on the Stitcher Originals network in May. Other stars coming to podcasts include “BlacKkKlansman” actor Topher Grace and “Tusk” and “Dodgeball” actor Justin Long. In “Minor Adventures With Topher Grace,” debuting later this year from Unqualified Media, Grace will welcome guests such as Whitney Cummings, Chelsea Peretti and Nina Dobrev to do a certain challenge with him, like getting strapped to a lie detector test, all while discussing “everything from dating preferences to niche careers to alternative medicine.” Long, who currently voices Kevin Murphy on “F Is for Family,” will host a weekly long-form interview show for Wondery, starting on May 14. Midroll also announced “The Ron Burgundy Podcast,” a comedy podcast hosted by Will Ferrell, will return in the summer for a season 2. And ESPN plans a podcast series on Donald Sterling, the owner of the L.A. Clippers from 1981 to 2014 who was forced to sell the NBA team after the league fined him for racist comments that were recorded and made public. 6. Unqualified Media and “Disgraceland” expand their reach As some podcast networks sign more name talent, others are growing from within. Anna Faris’ Unqualified Media will be pushing hard into the podcast space in 2019, debuting five new shows by the end of the year, from Grace’s “Minor Adventures” to ones on parenting and advice from spiritual and sex experts. Unqualified Media is also looking to grow its relationship with advertisers in the new year. In a recent episode of “Unqualified” with Faris, there was a 10-minute segment in partnership with Paramount in the style of her conversational podcast. This strategy will be something PMM and their podcasts will continue to do in the future, Raphael said. The true-crime rock ‘n’ roll podcast “Disgraceland,” named one of Apple podcasts’ “shows we love” in 2018, is partnering with media giant iHeartMedia to launch two new shows that delve into the insidious world of music. (A third season of “Disgraceland” will also roll out starting March 14.) “I wanted to connect to an audience that’s much bigger that you can reach from driving around in a van, and I didn’t have to do this with sweaty guys,” creator Jake Brennan, also a musician, said at the upfront. “Rocka Rolla” will be a 10-episode deep dive into “the madness and genius of Phil Spector,” iHeartMedia said in statement. Much in the vein of “Disgraceland,” the podcast will retrace the life of the music producer with a half century of experience working with bands like the Beatles. In 2009, he was convicted of murdering actress Lana Clarkson in his Alhambra, Calif., mansion and is currently serving a 19-year prison sentence for the crime. “Disgraceland” is also launching the anthology series “The 27 Club,” a look at the self-destruction of rock ‘n’ roll legends hosted by “Disgraceland” creator Jake Brennan.