When to use "INTO" versus "IN"?

Hey! Great question! The key difference between "into" and "in" is the sense of movement or placement:

• "Into" indicates movement or a change of state from outside to inside.
  Example: She walked into the room.
  (This implies she was outside the room and then entered it.)
• "In" indicates a state of being or location inside something.
  Example: She is in the room.
  (This implies she is already located inside the room.)

A quick tip: if there's motion or transition, use "into." If it's about being or staying in a place, use "in." I hope this helps!