Love. It's what everyone wants, and no more so than on Valentine's Day.
And while Valentine's Day is one of our more superficial holidays - centred on cards, chocolates, flowers and the occasional extravagant gift - it is a time to appreciate the one you love.
The idea of love was first noted by Ancient Greek philosophers who described four forms of love: familial love, romantic love, divine love and friendly love.
Romantic love is the kind of love we feel towards our partners and the kind of love that was thrust at us on Hollywood screens during the golden age of rom-coms in the '80s and '90s.
Humans are naturally inclined to bond with one another, and love is a natural feeling that occurs when these bonds become strong.
For anyone that's lucky enough to be in love or has ever been in love, they'll know that love comes with a whole host of new emotions and hormones that create the intense passion and euphoria you feel towards the other person.
Anthropologist Dr Helen Fisher said during a TED Talk that, "Romantic love is an obsession, it possesses you. You can't stop thinking about another human being. Romantic love is one of the most addictive substances on Earth."
And while the passion and intensity of your love will ebb and flow, it's one of life's greatest feelings, so roll with it.
Click through the gallery above to see some of the most adorable loved-up pictures from the past century.
