Recent biological research indicates that there is a biochemical basis to love, which explains why people in love feel as if they were in a more beautiful world. Psychologists such as Dr. Elaine Hatfield, Robert Sternberg and Zick Rubin posit that love consists of three or more stages. The three main stages are lust, attraction, and attachment, while some of the other stages are intimacy, trust, and jealousy. Each stage is ruled or initiated by specific hormonal controllers. In their studies, every love passes through some of these stages and occurs due to the mediation of certain molecules in these specific chemical controllers. Biological research has shown that the hormones dominant in the different phases include testosterone and estrogen (the sexual hormones); dopamine, norepinephrine and serotonin (these are the “pleasure chemicals” - the hormones invoking feelings of pleasure and excitement); and oxytocin (the “cuddle chemical” - the hormone producing feelings of attachment to another person). For example, in the second phase of attraction, when people have the feeling of being in love, the little molecule phenylethylamine (known as PEA), controlling the love chemicals dopamine and noreinephrine, can cause feelings of elation, exhilaration and euphoria. People feel excited and fulfilled. Additionally, biological anthropologist Helen Fisher, an expert on romantic love, discusses what happens in the brain when people are in love and proposes that there is a dramatic increase in the amount of dopamine and norepinephrine present in the brain when one first becomes infatuated with another person.