In The Science of Kissing, science journalist Sheril Kirshenbaum unravels the mysteries of kissing, and the evolution of this very human practice over the ages.

Sometimes, our words aren't enough to tell someone how we feel about them.

Throughout the ages, humans have expressed their affection in many different ways. Lovers wrote letters to each other, snuck out at night to meet in secret gardens by the moonlight, and serenade one another but kissing seems to always have been the staple of any good romance story.

Kissing has long been seen as a universal way of expressing romantic feelings.

In most romantic movies, the kiss is the moment the audience expects the most, because it makes the love story tangible. In fact, a quick Google of "top movie makeouts" generates hundreds of results.

Like satellite images where two galaxies merge and appear to be kissing, two lovers' lips touching seems to be a merging of two souls.

But where does this practice come from? Has it always existed, or did it evolve over time? It's funny how we can take this seemingly natural act for granted.

Here, writer and researcher Sheril Kirshenbaum unravels the secrets of kissing and gives you tricks to make sure you master the art.

Find out why we kiss, how the practice changes depending on culture, and discover science-backed evidence on how to make a kiss as good as it can be.