HBO’s limited series “Chernobyl” not only won 10 Emmys last month — it’s also been a huge hit as a behind-the-scenes podcast. The first episode of the podcast aired in early May, and — to the shock of everyone involved in it — quickly became the No. 2 podcast across all categories in iTunes. Now, said HBO senior vice president of digital marketing and content Jim Marsh, the podcast has generated more than 10 million plays. Netflix has also found stellar success with its “Behind the Scenes: Stranger Things 3” podcast.

The Wall Street Journal reports that “over the past couple of years, networks and streaming services have increasingly looked to the podcast world for content ideas, acquiring and adapting audio programs such as Wondery’s series ‘Dirty John’ and Gimlet Media’s ‘Homecoming’ into scripted TV series … [and] now, they are testing out podcasting themselves.”

“A lot of times, the stories about the craft of how a show or movie comes together ends up in the trades and stays locked in Hollywood a bit,” said Netflix vice president of brand and editorial Eric Pallotta. “I like how the podcast space opens up the access to those types of stories to anyone.”

Netflix plans to debut a behind-the-scenes take on Martin Scorsese’s “The Irishman,” which debuts in November, and another unnamed project. HBO is also “fielding inquiries from several showrunners.” “It’s important that we don’t do too much too quickly and be selective about the creators and partners that we work with,” said Marsh.

Other content creators are also looking to podcasts; CBS Studios plans to debut “Prime Directive: The Official Star Trek Podcast” on CBS All Access, including a new animated series “Star Trek: Lower Decks.”

WSJ notes that “the rise of the companion podcast is a twist on a well-established genre of commentary programs … [but] the main difference is that the new companion podcasts are produced by the networks themselves, and can leverage relationships with a show’s creators, writers and actors.”

But companion podcasts — “delicate marketing exercises, intended to envelop viewers in behind-the-scenes content in a way that doesn’t feel like marketing” – have their challenges. HBO and Netflix, as subscription-based services, don’t run ads, although podcasts can cost $10,000+ per episode. An additional expense is marketing the podcast to listeners.

“In a time when content discovery is a huge challenge for networks, developing a companion podcast is increasingly viewed as a worthwhile investment, not just to draw attention to the show, but, the thinking goes, to inspire podcast listeners to buy monthly subscriptions,” concludes WSJ.