An embryo turns itself inside out in a new first-of-its-kind video released by medical researchers at the University of Cambridge. The embryo, of a type of algae called Volvox, is seen morphing from a ball into a mushroom-like shape, then back into a sphere.

The algal embryo could provide biologists with a better understanding of early fetal development in animals.

During gastrulation, the developing embryo folds upon itself, taking on a form similar to a thimble. The first few layers of cells that will form the different organs in the body begin to form. Animals, including humans, undergo a similar process to that seen in Volvox. However, the activity in animals, driven by a myriad of cell changes, is exceedingly difficult to track. Unlike animal embryos in their earliest days of development, these algae completely turn themselves inside out during the process. The simplicity of the organism, combined with their full return to a sphere-like shape, makes them an ideal object of study for researchers studying embryo development in animals.

Gastrulation is sometimes referred to by biologists as the "most important time in your life."

Over the course of about an hour, the embryo was observed folding in on itself, forming a pair of hemispheres. One half then folds into the other half, which engulfs its twin. The outer shell continues to move over its partner until the embryo is once again in the form of a sphere.

"Until now there was no quantitative mechanical understanding of whether those changes were sufficient to account for the observed embryo shapes, and existing studies by conventional microscopy were limited to two-dimensional sections and analyses of chemically fixed embryos, rendering comparisons with theory on the dynamics difficult," Raymond E. Goldstein of the University of Cambridge said.

Before this study, researchers knew that certain changes in the shapes of cells were associated with various stages during this process of development. However, critical questions were still left unanswered about this sequence of events. For instance, how do the cells decide which hemisphere engulfs the other? The study noted that one half of the pair would have to contract while the other half expanded to create the mushroom shape observed by researchers.

"It's exciting to be able to finally visualize this intriguing process in 3D. This simple organism may provide ground-breaking information to help us understand similar processes in many different types of animals," Stephanie Höhn, lead author of an article detailing the results of the study, said.

A video showing gastrulation is shown below and also is available on Cambridge University's YouTube channel.

Study of the embryo turning itself inside out was detailed in the journal Physical Review Letters.