28 June 2021

Structural colour: More than meets the eye

How microscopic structures create nature’s most dazzling colours.

By Yosola Olorunshola

A collage of luminous blue butterfly wings

Ever wondered how the feathers on a peacock or hummingbird achieve their signature glint?

Or why some leaves give off a silvery shimmer, even in low light?

The secret lies in structural colour – an evolutionary process involving microscopic structures that reflect and refract light in unique ways.   

Transparent materials are sculpted in patterns invisible to the human eye. These structures work like tiny prisms or holograms (like the security strip on a bank note) to bend and reflect the light back into our eyes. 

Fronds of the Selaginella fern reflect a metallic blue glimmer
Microscopically thin layers of transparent material in the leaves of the fern Selaginella reflect back light rays we see as blue. (Selaginella fern © Andrew Parker)

The result is what we know as 'structural colour'.  

Structural colour often appears as the brightest form in nature, characterised by a dazzling metallic sheen. It is 100 per cent reflective, so it can even be seen in the deep sea.  

Here are three mesmerising examples of structural colour at work in nature.

Hide and seek  

The different layers of an abalone shell capture the evolutionary purpose of colour.  

As a marine snail, its shell is made up of many microscopically thin layers to make it strong and robust.

Two abalone shells sit side by side. On the left, the camouflaged outer shell is visible, while on the right, the iridescent blue and green sheen of the inner shell is visible
(L) Camouflaged outer shell, (R) Inner shell pattern produced by structural colour. (Abalone shell © Andrew Parker)

These transparent, thin layers also reflect light and become a form of structural colour.  

However, this bright colouring would do more harm than good if it were visible to predators, alerting them to the abalone's presence. 

Instead, a dull, pigmented covering (above left) has evolved as a form of camouflage to conceal the naturally brilliant colour beneath (above right).  

Silver lining   

The silver and blue colours of the Begonia rex ‘Silver Cloud’ result from the selected reflectance of sunlight by microscopic structures in the leaves.

The reflection of rays of all wavelengths in white light produces its silver sheen.  

The silver frost-like appearance of the leaves of a Begonia rex
Begonia rex © Andrew Parker

However, too much water in these leaves destroys the structural colour machine.

As a result, the green pigment chlorophyll sometimes dominates what the eye can see.  

Beating wings  

Hummingbird feathers contain microscopic structures that very precisely reflect sunlight – a natural form of nanotechnology that dates back thousands of years.  

recent study uncovered this insight, revealing the unique structures within the cells that make up hummingbird feathers.

These structures are distinct from other birds as they are shaped like pancakes and contain lots of tiny air bubbles, creating a more complex set of surfaces that allow light to bounce off in different ways.

Two hummingbirds feeding on bright pink flowers
This iridescent effect is the result of the special shape of the pigment structures within the cells of a hummingbird's feathers. (© James Wainscoat / Unsplash)

The result is the majestic gleam that make hummingbirds so recognisable. 

Now a new technology, Pure Structural Colour, developed by scientist and artist Andrew Parker, offers an opportunity to recreate these luminous colours on a practical scale for the first time.  

As a form of bioinspiration – an innovation inspired by a natural process – Pure Structural Colour represents a unique tool to showcase the relationship between science and beauty in vivid colour.  

Visit Naturally Brilliant Colour at the Shirley Sherwood Gallery of Botanical Art this summer, and explore the potential of this invention to help us see nature with fresh eyes. 

Discover more

Continue the adventure into colour with these kaleidoscopic reads.

Naturally Brilliant Colour exhibition

Naturally Brilliant Colour

Summer 2021: Experience colour like never before in an exhibition that celebrates the spectacular shades of the natural world.