Even if you're not a parent, or even plan to have kids, this video is pretty cool to watch.
It's of a fetus yawning at 30 weeks of pregnancy.
Researchers at Durham and Lancaster Universities in England have been studying yawning inside the womb, trying to figure out why fetuses do it.
The scientists used 4D ultrasound scans, which stitch together pictures taken from a variety of angles to create clear three-dimensional images.
The scientists captured a quick series of images of 15 fetuses - eight female and seven male.
All of them were healthy and scanned for 20 minutes, at various stages of pregnancy - 24 weeks, 28, 32, and 36 weeks.
After that, the scientists went through the images frame by frame and counted the yawns and other movements.
Over 58 scans, the researchers recorded 56 yawns and 27 other mouth movements - with no real difference between females and males.
They also noticed something particularly striking. The amount of yawning decreased steadily through the pregnancy.
At 24 weeks, for example, the fetuses yawned about two times every 10 minutes. By 36 weeks, the yawning had stopped.
So, what does it mean? Well, scientists think the yawning could be related to the maturing of the fetus' brain and its central nervous systems.
"It may be that, in order to get part of the brain to mature in the correct way, you need a certain stimulus, and yawning might be that stimulus," said Nadja Reissland, a psychologist who specializes in fetal development at Durham University.
"Unlike us, fetuses do not yawn contagiously, nor do they yawn because they are sleepy. Instead, the frequency of yawning in the womb may be linked to the maturing of the brain early in gestation," Reissland said.
The researchers say the more they can find out, the more it could help doctors monitor the normal development of a fetus in the womb.
Last year, the same group of scientists were part of a study that suggested fetuses develop facial expressions in the womb, similar to crying and laughing.
According to ultrasound scans of two females fetuses, those kind of expressions showed up between 24 and 35 weeks.
The scientists now hope to scan more fetuses to understand the yawning more.
They also hope to study fetuses who are exposed to cigarettes or drugs, or are diagnosed with specific medical conditions.
The findings are published in the journal PLoS ONE.