Phase-change memory's 40-year journey from bright idea to mobile phone. Is phase-change memory about to appear in your mobile phone?Samsung South Korean manufacturer Samsung Electronics announced this week that it has begun mass production of a new kind of memory chip that stores information by melting and freezing tiny crystals. Known as phase-change memory (PCM), the idea was first proposed by physicists in the 1960s. Here, Nature explains how PCM works, why it has taken so long to develop and how it could change your mobile phone forever.What's the big idea behind PCM? PCM was first proposed by physicist and...