In 2008, was the fourth largest online dating site, based on number of singles available; largely due to a successful ad campaign targeting e Harmony (#5 largest dating site) and their anti-gay Christian-only, who regect people who aren't happy all the time (adjacent video).
 uses information such as middle-finger-to-ring-finger length ratios (digit ratio), an indication of testosterone levels, and personality type matching assessments, such as by asking people "do you like to count things"; counters have high dopamine levels and tend to be the "explorer type".
I like the idea of research and measurement around these things that seem so impossible to quantify."  Wall Street Journal editor Emily Parker, who interviewed Waldorf, reasoned to herself “of course, this only leads one to wonder, how does one measure interpersonal chemistry?
The e Harmony app is a replacement for the full website; in fact, likely due to some Flash (s adbe) error on my Mac (s aapl), the i Phone app was the only way I could upload my photo. Sometimes, the e Harmony Mail wouldn’t go through on the i Phone.
It would send it, but then it would disappear from my sent mail items, apparently having gone nowhere at all. The app is also a Universal app, and I love how it app opens to a dashboard instead of directly into the Mail view (unlike other apps — read on). Plenty of Fish’s app seems to play to the site’s focus of immediate communication — unlike e Harmony, Plenty of Fish starts off with messaging your prospective suitor. The font is a tad smaller than it is in the i OS Mail app, and the overall feel of the message pane is cramped.
By having singles send in saliva samples, the site facilitates a laboratory analysis of each person's immune system type and, using this data, claims to create optimized “physical chemistry” or "sexual chemistry" between people based on the sweaty T-shirt study, a pattern, discovered in 1995, which finds that people are most attracted to the smell of people who have the most-dissimilar immune system.
 The site was conceived by Holzle, a long-time internet site dater, after watching a TV discussion on the findings of the sweaty T-shirt study.
The site e (Alexa-rank: 1,100) founded in 2000 by American psychologist Neil Warren and Greg Forgatch, whose vision is not simply to create marriages, but to create happy marriages by using scientific research to unite compatible individuals.