What happened when Alice ran after the rabbit?

Alice running after the rabbit is the event that causes her adventures in Wonderland to begin.

She sees it pop into a rabbit hole, and, without thinking, follows it in. The rabbit hole goes on for some way, but then dips suddenly, and Alice finds herself falling down a deep well, which terminates in Wonderland. There is no way for her to go back, so she is more or less obliged to explore her new surroundings, which leads her to have some extraordinary experiences, and meet some extraordinary people.