When we hear two people in love, you will hear the word chemistry. According to neuroscientists, dopamine levels increase.
Dopamine is one of those chemicals that help transmitting signals in between the nerve cells (neurons) of the brain.
It is a neurotransmitter. In other words, it controls communication in the brain.
This is the chemical which gets you feeling thrills and all excited when you see your newly beloved or craved to be with him or her.
The other neurotransmitter called serotonin which is responsible in making people with depression feel sad, the levels drop. But increases your desire.
Besides this, your cortisol levels go up. Cortisol is a hormone that is released in response to stress. When you are in love, it can a very stressful time as well.