Falling in love produces dopamine and endorphins. Dopamine is produced from happiness and makes people happier; endorphins are produced from pain and have analgesic effects. Endorphins are like the rainbow after the rain, and dopamine is like the beautiful sunset and beautiful flowers.

Because love can be both sweet and painful, dopamine and endorphins are produced. Dopamine is a reward mechanism: if you do something, you will be rewarded, which will give you pleasure and hope you can do it again next time. Endorphins are a compensation mechanism: when you feel uncomfortable doing something, compensate for it, giving you a sense of pleasure, allowing you to persist, and not be afraid to do it again next time. In addition, dopamine is the reward, motivation and pleasure center of people, and endorphins are born from pain and can relieve pain.

Dopamine is called the "love substance", while endorphins are called the "marriage substance."

During the ambiguous period, a love substance called phenylethylamine will be secreted in the brain; during the passionate love period, dopamine will be secreted, giving people a feeling of sweetness and happiness. However, the peak concentration only lasts for four years, so it is not advisable to fall in love for more than four years. After getting married, endorphins will be secreted, giving people a warm and comfortable feeling.

When a man and a woman long for each other for the first time, phenylethylamine will be released. If this desire continues, when they fall into love, they will secrete dopamine and seroamine. Serum amine is also in love. The most important substance in the world can make people in a state of near madness for a while. In the next stage, men and women will continue their relationship.