This picture shows the heart of a two-day-old zebrafish.
Its striking beauty has seen it win the Mending Broken Hearts prize in the British Heart Foundation's competition for outstanding images and videos from the research it funds.
The image was produced by Dr Jana Koth as part of her research at the MRC Weatherall Institute of Molecular Medicine at Oxford University.
Under the microscope, it is possible to see individual cells and the internal organization of the early heart as it grows and develops. The green cells are heart muscle cells, and the red and blue staining shows components that make up the muscle. The heart consists of two sections – the large, thin atrium (where blood flows in) and the smaller, thicker ventricle (where blood leaves the heart).
Remarkably, the hearts of zebrafish can repair themselves after damage, something which human hearts cannot do. The hope is that understanding this ability might in the future allow ways of prompting heart repair in people who have had heart attacks and develop heart failure, an area of research known as 'regenerative medicine'.
On winning the prize, Jana said: 'I'm stunned and delighted to receive this year's Mending Broken Hearts award. In the course of our regenerative medicine research we produce images like this all the time. They help us to uncover the secrets of the zebrafish. It's great to be able to take a step back and admire the beauty, as well as the biology, of this natural wonder.'