Leonard (Johnny Galecki) and Penny (Kaley Cuoco) are The Big Bang Theory's core couple. Sheldon (Jim Parsons) and Amy (Mayim Bialik) and Howard (Simon Helberg) and Bernadette (Melissa Rauch) may have more going on right now, what with engagements and babies and things of that nature, but LenPen is the heart of the show. The show's romance started with them, and they've been the rock for almost a decade.

In honor of them, we've compiled their most romantic moments, from their first kiss to their wedding. They've come a long way from being the aspiring actress and the nerd across the hall; now they're the successful pharmaceutical sales rep and the nerd who loves her.

The next step in their relationship is having a baby. We don't know when that will happen, but when it does, it will be cause for celebration.

The Big Bang Theory airs Thursdays at 8/7c on CBS.

(Full disclosure: TV Guide is owned by CBS.)