Enter somewhere or something; also fit inside something. For example, Don't go into this building, or The tractor is too big to go into the shed. [c. a.d. 1000]
Enter a particular state or condition, as in She's about to go into hysterics, or I'm afraid he went into a coma. [Second half of 1600s]
Investigate or discuss, especially in detail. For example, We haven't time to go into the entire history of the project. [Early 1800s] Also see enter into, def. 4. Also see the subsequent entries beginning with go into.
Dictionary.com presents 366 FAQs, incorporating some of the frequently asked questions from the past with newer queries.