Multicoloured 'brainbow' shows nerve activity
The image, dubbed the "brainbow", shows in detail how different parts of the brain interact and mature.
Scientists hope the images will help them identify how brain wiring goes awry in many different diseases.
The brainbrow: Shows nerve activity
The multicoloured pictures are made by tagging individual neurons in the brain with about 90 different colours.
Dr Jeff Lichtman, one of the US researchers from Harvard University in Cambridge, Massachusetts, said: "In the same way that a television monitor mixes red, green, and blue to depict a wide array of colours, the combination of three or more fluorescent proteins in neurons can generate many different hues.
"There are few tools neuroscientists can use to tease out the wiring diagram of the nervous system; brainbows should help us much better map out the brain and nervous system's complex tangle of neurons."
Colourful: The images are made up of 90 colours
Brainbows could also help track the complicated development of the mammalian nervous system, which is still not fully understood.
This in turn may clarify the origins of many brain disorders that arise early in development.
The technique shuffles genes encoding for green, yellow, orange and red fluorescent proteins.
Once "switched on", the genes light up the neurons they have been inserted into in a glorious array of colours.
The scientists describe the work in the latest issue of the journal Nature.
They used brainbows to study neural circuits in mice for periods as long as 50 days.
Already, they have discovered previously unrecognised patterns of neural arrangement.
Professor Joshua Sanes, another member of the Harvard team, said: "As far as understanding what we're seeing, we've only just scratched the surface."
Bright: The images have been likened to artwork
Vivid: The new method creates a bright image