A six-part BBC series looks at the newest research from around the world to find out what could it be that makes us happy.
We all want to be happy but the problem has always been that you can't measure happiness.
Happiness has always been seen as too vague a concept, as Lord Layard, Professor of Economics at the LSE and author of "Happiness - lessons from a new science" points out.
"There is a problem with the word happiness.
"When you use the word happy, it often has the sort of context of balloons floating up into the sky or something frivolous."