If you are researching the purchase of a youth or child helmet you may find that the same helmet design comes in two options- one in "MIPS." MIPS stands for "multi-directional impact protection" and adds an additional safety technology to the helmet. It used to be found almost exclusively on high end helmets, but now is now almost ubiquitous at all price points. In essence MIPS adds an additional layer that allows the helmet to slide, reducing rotational impact forces. It is a bit of a gross analogy, but it mimics how the skin can protect the brain by lubricating the impact.
Youth or child helmets are generally much less expensive compared to adult helmets, so the MIPS version is relatively more expensive adding $10 or more to the helmet. But as the father of four I believe this is worth every penny. Kids fall, crash, wreck, and generally get hurt much, much, much more than adults. This is how they learn and it is nerve racking to watch. It is much more likely that the MIPS technology incorporated into a helmet will actually be used. Kids also crash in a wide variety of ways, doing a wide variety of things. I watch my kids go from bike, to scooter, to pedal car in the same 10 minutes. About 7 percent of kids ago 3-17 experience a head injury, and the percentages rank higher with age. About half a million kids end up in the emergency room each year with a head injury. These stats alone recommend using every available option to protect your kids noggin.
Of course wearing the helmet is the most important thing, next is making sure it is adjusted and fitted properly, but if you are wondering if you should spend the extra money on a MIPS helmet for your kids it is a no brainer.