Patent fight comes to US court

On Monday, tech giants Apple and Samsung will finally appear in court in California for the latest - and the most important - phase of their long-running worldwide patent fight. Between them, these two companies make over 50% of the world's smartphones. The result of the case could cost the losers hundreds of millions, or even billions, of dollars, while the winners could gain a major advantage in the smartphone and tablet wars.

But while the case could be one of the most important patent disputes for decades, it's also rather complex - and it's far from the only patent battle the smartphone world has seen in recent years. What are they actually fighting over? Just who is suing who? And frankly, isn't it all a bit of a mess? We try to explain...