Million Whys

Million Whys is a micro-learning app built around single-question knowledge cards. Each card asks one question, offers three choices, and then explains the mechanism behind the answer — so a session takes about ten seconds but leaves you with an explanation rather than a fact to memorize.

The core loop is a daily set of questions with a streak counter. Scores are grouped by topic tag rather than one global ranking, so you can end up ranked in a specific subject rather than competing with everyone on a single axis. There is also an asynchronous challenge mode: generate a set, send a link, and whoever opens it plays the same questions.

Create mode lets you point the app at any topic and get a small quiz pack generated on the spot — type a question, or photograph something in front of you, and it builds cards and explanations about it. This part is explicitly AI-generated on the user's request. The wider question bank is mixed: some cards are editorially prepared and fact-checked before publication, others are model-generated, and the illustrations are AI-generated.

A secondary screen, Curiosity Sky, maps the roughly 2,600 topic tags in the bank as a star field, lighting up the areas you have answered correctly — a progress view that shows coverage instead of a percentage.

Content spans science, nature, history, psychology, technology and everyday phenomena. It is not exam prep: there are no lesson plans, no standards alignment and no grade tracking.

Free to use, with no ads. Play is limited by a stamina system (five plays, one regenerating every twelve hours) which caps a session rather than a day; an optional subscription removes that limit. Available on the web, iOS and Android, in English and Chinese. The daily question is also playable on the web with no account at all at millionwhys.com/trivia-question-of-the-day.