Scarce as they are, these two metals are necessary for our survival, playing essential roles in human growth and metabolism. But one place we wouldn't expect to find either is clumped inside our brain cells.

A team of researchers from the US and UK spotted the tell-tale glint of copper and iron in their elemental forms using a form of X-ray microscopy (STXM) on samples of neural plaques taken from the frontal and temporal lobes of Alzheimer's patients.

To build a bigger picture of how these two metals might be involved in dementia, a research team led by scientists from Keele University in the UK hunted for signs of iron and copper inside resin-embedded amyloid plaque cores donated by two Alzheimer's patients.

Not only did they spot accumulations of iron and copper, but these metals were in elemental forms, essentially forming tiny deposits buried deep inside the amyloid plaques. What's more, the team could tell a few things about the metals' ability to react with other substances.

But this is the first time anybody has uncovered tiny pieces of copper in elemental form inside human neurons.