What's so important about neurotransmitters?

The brain is a delicate network of a trillion neurons. The firing of these neurons enables us to think, to move, and to act. Neurotransmitters are chemicals outside the neurons and between them which allow for neurons to "communicate" with each other. Because of their key role in the brain, it is a serious problem when neurotransmitters are not functioning properly. Many poisons and drugs affect the brain by affecting neurotransmitters. Similarly, neurotransmitter dysfunction is now recognized as a component of behavioral disorders ranging from Alzheimer's disease to schizophrenia.

If scientists discover a difference between men's and women's brains, doesn't that mean that men and women by nature are different, and not much can be done to change it?

There do seem to be some fairly consistent differences between male and female brain structure, but the relationship between brain and behavior is not so simple. First, while two people may use different parts of the brain to accomplish a task, the performance outcomes may be identical. Second, our brain development is shaped by our environment. People who receive greater stimulation of one kind or another encourage development of that part of the brain. Thus, differences in male and female brains may be a result of culture, not biology.