This rare flower in Japan turns completely transparent when it rains and looks like glass

At first glance, it looks like any other woodland wildflower. Delicate white petals surround a cluster of bright yellow stamens, swaying gently beneath the canopy of cool mountain forests. But when rain begins to fall, something extraordinary happens. The flower's snowy petals slowly lose their colour and become almost completely transparent, as though they were made of glass.

Known as the skeleton flower or crystal flower, Diphylleia grayi is one of the most unusual flowering plants in the world. Native to the moist mountain forests of Japan, China and parts of eastern Asia, the species has fascinated botanists for decades because of its remarkable ability to change appearance when exposed to water.

This rare transformation, driven by the microscopic structure of its petals rather than any pigment change, has made the plant a striking example of nature's hidden optical engineering.

Why does the skeleton flower become transparent when it rains

Unlike many flowers that rely on pigments to produce colour, the white appearance of skeleton flower petals comes largely from the way light interacts with microscopic air spaces within the petal tissue.

Researchers from the School of Materials Science and Engineering, Nanyang Technological University studying flower optics via a study titled ‘Diphylleia Grayi Inspired Stretchable Hydrochromics with Large Optical Modulation in Visible-Near Infrared Region’ have found that white petals often scatter light because tiny pockets of air are trapped between plant cells. This scattering causes the petals to appear bright white to the human eye.

When rainwater soaks the petals of Diphylleia grayi, those air pockets become filled with water. Because water and plant tissue have similar optical properties, the scattering effect is greatly reduced. Instead of reflecting light in many directions, the petals allow much more light to pass through them, creating the striking transparent appearance.

Once the flower dries, air returns to these microscopic spaces and the petals gradually regain their familiar white colour.

This transformation is a natural optical phenomenon rather than a chemical change. The flower does not produce new pigments, nor does it alter its cellular structure permanently. It simply changes how light travels through the petal.

A woodland plant adapted to cool mountain environments

Diphylleia grayi belongs to the family Berberidaceae and typically grows in cool, shaded forests with abundant moisture. The plant is especially associated with mountainous regions of northern and central Japan, though populations are also found in parts of China.

The species produces large umbrella-like leaves that can reach more than 40 centimetres across. In late spring and early summer, clusters of small white flowers emerge above the foliage. These blooms are relatively short-lived, but their dramatic reaction to rain has made them famous among botanists, photographers and nature enthusiasts.

The plant was first scientifically described in the nineteenth century and named in honour of the American botanist Asa Gray, one of the most influential figures in the study of North American flora.

Scientists are studying the flower's natural optical engineering

The transparency effect of the skeleton flower has attracted interest beyond botany. Researchers investigating biomimicry and optical materials have examined how the petals manipulate light so efficiently.

The flower demonstrates how microscopic structures can dramatically alter appearance without relying on pigments or chemical reactions. Similar principles are being explored in the development of advanced transparent materials, water-sensitive coatings and optical technologies.

While Diphylleia grayi is not the only plant whose appearance changes when wet, few species display the phenomenon as dramatically. The transformation can occur within minutes during rainfall, turning an ordinary white flower into a crystal-clear bloom before reversing once the sun returns.

For visitors hiking through the misty mountain forests of Japan or China, the sight can be startling. A cluster of white blossoms disappears into the rain, replaced by petals so transparent that only their veins remain clearly visible. It is this delicate network of veins that inspired the common name "skeleton flower", making the plant one of nature's most remarkable examples of optical illusion.