Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Input: Passage: In multicellular organisms, specialized cells may be organized into tissues. Tissues may be organized into organs, and organs may be organized into organ systems. Organ systems work together to carry out all the functions of the whole organism. Answer: tissues
Output:
In multicellular organisms, specialized cells may be organized into what, which in turn may be organized into organs?