It's the frightening internet craze which has been hitting headlines up and down the country.
But what exactly is the "Momo Challenge" and why do we need to be aware of it?
There are a number of different origin stories about the so-called "challenge", which is now said to have hit the UK.
Seen to be a form of cyberbulling which spreads through use of social media and mobile phones, the "challenge" sees users targeted by a contact named "Momo" before being sent distressing messages and images, or encouraged to perform dangerous acts.
"Momo" has also become associated with a viral picture of a woman, with long, dark hair and a distorted face, described by some as the "character" of the craze.
The picture has been shared widely on social media.
There have been reports of young people being contacted through WhatsApp by a user named "Momo", as well as scary clips being cut into child-friendly videos on YouTube.
According to national media reports, some schools across the country have sent warnings to parents about the "distressing" content involved in the "challenge".
National Online Safety, which provides support and resources to UK schools and educates on online safety, has issued an advice document on what the challenge is, and how to keep young people safe from it.
Tips include setting up parental controls for devices in the home, reporting and/or blocking harmful material you encounter online and speaking to your child's school.
The document said: "Trends and viral challenges can be tempting for children to take part in; no matter how dangerous or scary they seem.
"Make sure you talk to your child about how they shouldn't succumb to peer pressure, and do anything they are not comfortable with, online or offline."
The guide from National Online Safety also encouraged parents to reassure their children that "Momo" is not a real person and cannot harm them, and speak regularly about their online activity.