Sometimes you need a reason to give another person a kiss. And, as was the case in probably the most famous kissing photo of all time, that reason can be a big one (victory in World War II). But, other times, a kiss is its own reason to celebrate.

Whatever you want to call it — a peck, a smooch, a snog — a kiss communicates love in a way that few other acts can match. How people started kissing is a mystery and why we do it is complicated, but, from a child’s sweet kiss to a lover’s sexy kiss (or a walrus’ whiskery one, as the case may be), the act is a language of its own. And a photograph of a kiss, it follows, captures that feeling.

Here, with a look back at 40 years of kisses from LIFE Magazine’s archives of iconic 20th century photography, that fact is as clear as ever.