Throughout your life you go through many remarkable（异常的） phases（月相） of metamorphosis. And none of them are as uncomfortable as when you morph from the adorable, pudgy caterpillar（毛虫） of childhood and spread your wings as an awkward（尴尬的） teenage butterfly. Not only are our bodies flooded with signals to become sexually（性别地） mature（成熟的）, hair starts growing in strange places, voices change, your emotions are all over the place, your bodies are growing in every which direction, so many secretions（分泌）. All of these changes, as well as dozens（一打） of others that you experience on timescales（ 时标） ranging（（在内）变动） from seconds to years, are mediated（调解） by one of the strangest systems in that already peculiar（特有的） sack（大袋） of meat you call a body, the endocrine（内分泌的） system and its hormone（荷尔蒙） messengers（送信者）. To understand why this chemical soup exists, we first need to think about the Mongol Empire（帝国）. Wait, what?

  Hey smart people, Joe here. So, the Mongols. Kubla Khan in the mid-1200s reigned（统治） over the largest empire（帝国） in history up to that point. And he had a problem. Let's say Kubla, Mr.Khan, number K, had an idea. How do you get it to the farthest reaches（范围） of your empire（帝国） and make sure that every distant（在远处的） feudal lord works together for the good of the whole?

  Not to mention, how do you keep stability（稳定性） in your vast（巨大的） empire（帝国） before the age of light speed communications? He sent emissaries to deliver his message and make sure that it was carried out. Your body has the same problem. It has to send instructions to its distant reaches to coordinate（使协调） stability（稳定性）, peace and responses to the external（外部的） environment. Not even the occasional（偶然的） invader（侵略者）. But instead of emissaries and ambassadors（大使）, your body sends out tiny chemical messengers called hormones.

  And instead of roads, they travel through your circulatory（循环的） system to find the cells（细胞） or organs（器官） that need to heed their message. Hormones tell us many things, including when we're hungry, when to sleep, when dangers near, and even when to grow into a new body. This problem of how to send messages over long distances and across hugely（巨大地） varying（改变） time scales（刻度） is one that's likely even older than multicellular life. This is a cellular（细胞的） slime（黏液） mold（模子）. They start life as individual amoeba blobbies, but when their environment gets stressful, like when there's not enough food, they secrete（隐秘） a chemical signal that tells them to pile（堆叠） up with their neighbors until they slither（不稳地滑动） together like a single slimy slug. Thousands of amoebas act together like one, like minions to their chemical messenger overlord, eventually even morphing into weird（怪异的） tree-like structures that allow a few lucky individuals to escape as spores（孢子） do better and more fruitful（多产的） land.

  Now, you might not think you have a lot in common with a slime mold, but they're faced with the same problem your body is. How do you get many individual cells to communicate, coordinate, and cooperate（合作） over long distances and even undergo（经历） major changes? The answer, secreted chemical messages. I mean, think about it, that chemically（用化学） induced（劝诱） slime（黏液） mold（模子） metamorphosis isn't that unlike what happens during puberty. I mean, you just live in your life and then bam, your body's flooded with chemicals, setting off a series of weird and wonderful changes. This gradual（逐渐的） and irregular readjustment of the glandular（ 腺状的） system is almost certain to make Johnny nervous, excitable, and a little emotionally（感情上地） unstable（ 不稳定的）.