In a crowded children’s streaming video space, Houghton Mifflin Harcourt has announced that its year-old SVOD learning app Curious World has surpassed the one-million download mark in the US.

Featuring short-form videos, games and books curated by early learning experts, the kid-safe iOS platform recently added 56 original kids series to keep pace with major streaming competitors like Netflix and Amazon, as well as emerging services such as Hopster and PlayKids. In total, Curious World features 1,000 pieces of original and licensed content.

Among the first six original short-form titles that launched since February are music video series A Rhino Named Paul (pictured), animated language-learning series Jingle Bilingual, how-to costume series Recycled Superheroes and live-action arts & crafts program Get Crafty.

Curious World, in partnership with Blue Zoo and WGBH, will debut another new original series called Mac & Izzy next month.

The app’s third-party content includes Disney Sound’s They Might Be Giants, JibJab’s StoryBots, Skyship Entertainment’s Super Simple Songs and Kit^n^Kate from Planet Nemo Animation and Ankama.

Additional licensed content is supplied by National Geographic, Caspar Babypants, PBS Digital Studios, Radical Sheep and Young Rembrandts.

Curious World will be at MIP Jr. and MIPCOM looking for new production and co-production opportunities that could help expand the app’s global user base.