The term 'FIT ONE INSIDE THE OTHER' can be summarized by the crossword solution 'NEST'. Nesting is a common practice in which one object is placed inside another, usually for storage or organization. This is often seen in kitchenware such as bowls and cups, or in furniture such as tables and chairs. Nesting is also used in many other contexts, such as nesting dolls, where one doll is placed inside another.