Refer to the passage below and then answer the question afterwards in the same language as the passage:

Passage: There are many species of bacteria and other microorganisms that live on or inside the healthy human body. In fact, 90% of the cells in (or on) a human body are microbes, by number (much less by mass or volume). Some of these symbionts are necessary for our health. Those that neither help nor harm humans are called commensal organisms.

Question: How much of the human body do microbes make up?
90%