Michelle and Oliver open the series with perhaps the biggest question of all – asking ‘What is Happiness?’.

Serving as an introduction to the subject we hear from neuroscientist Ash Ranpura who lays out the science behind four key neurochemicals in the body and reveals why they’re crucial in helping us understand happiness. Victoria Milligan lays bare her tragic story of losing her partner and child in a boating accident and how eventually it led her to truly appreciate life. And finally, Michelle calls on one of the world’s leading happiness experts, who’s racked up millions of views for his TED talk and who also just happens to be her husband, Shawn Achor. How does Shawn define happiness? At the end of the episode Michelle talks listeners through a quick and easy gratitude exercise called The Doubler.

Michelle and Oliver unpick the science behind strategies to make ourselves happier, with the help of leading psychologist in the field Professor Sonja Lyubomirsky from the University of California. We hear from British author Helen Russell who moved to Denmark when her husband got a job with Lego, and quickly discovered why the Danish way of life is so conducive to happiness. And Michelle shares one of her favourite daily exercises that helps train the brain to think more positively.

Research shows that Americans invest more time, money and emotional energy into the ‘pursuit of happiness’ than any other nation, but they’re sliding down the global happiness scale. Are these two things linked? We ask British author living in LA, Ruth Whipmann why she thinks they are, and what she’s discovered really DOES make us happy.

And ex-boy-band member Harry Judd (from McFly) tells us how exercise helped relieve his battle with anxiety and OCD and why he thinks more people need to understand the link between exercise and happiness.