What’s the main idea of the passage?

Like people who share news via Twitter, Facebook and Linkedln, cells, too, make use of multiple modes of information exchange. Some send out hormones, which travel far and wide via the bloodstream; others emit neurotransmitters, which carry signals between one neuron and another. But virtually all cells network with their neighbors via extensive collections of channels that directly connect the inside of one cell with the inside of the next.

History shows that there is a deep-rooted human urge to make a quick profit without working for it by trading in paper assets. One of the first documented boom-bubble-bust cycles was the "tulip craze" that took place in Holland in 1636 — 1637 when buying and selling tulips became a national mania that led otherwise rational people into mortgaging their worldly goods to invest in tulips.