里面

In a sentence

• 箱子里面有一本书。

  There is a book inside the box.

  Here, '里面' denotes the interior of the 'box', indicating its spatial position as containing something.

• 画的里面有一些隐藏元素。

  Inside the painting, there are some hidden elements.

  In this sentence, '里面' specifies the inside area of an artwork, emphasizing contained aspects of it.

• 问题的核心实际上在它的概念里面。

  The core of the problem is actually within its concept.

  Here, '里面' metaphorically refers to the internal aspect of the 'concept', signifying a figurative use.