Neurotransmitters

“Even though it is common knowledge, it never ceases to amaze me that all the richness of our mental life - all our feelings, our emotions, our thoughts, our ambitions, our love lives, our religious sentiments and even what each of us regards as his or her own intimate private self - is simply the activity of these little specks of jelly in our heads, in our brains. There is nothing else.” -V.S. Ramachandran

Brain cells. Source:University of Rochester

Some organisms are nothing more than one cell. These tend to be microscopic like bacteria, have short lives and a very restricted repertoire of behaviors. In comparison, multicellular organisms can reach thousands of mets (honey fungus), live virtually forever, (lobsters) and pilot space shuttles (humans). To achieve this complexity, they have to overcome one particularly daunting task: coordinating all their cells.

[Source: Nicholas Wright]