For a while, lots of people thought this mild, pleasant scent was just baby powder or sweet-smelling wipes.

Others claimed it was just a myth, a hallucination by sleep-deprived new parents.

But, just like new house smell and new car smell, new baby smell is real!

But what exactly causes this special scent, and why do scientists think it might be an evolutionary benefit for mothers and their babies?

Our body odors are made of lots of different secreted chemicals, but it’s hard to figure out how each one contributes to our natural smells.

And newborn baby smell is extra hard to study, because the scent is usually gone after about 6 weeks.

Researchers think one factor could be leftover amniotic fluid, which is the protective substance that surrounds the embryo as it grows.

Plus, there might be traces of vernix caseosa, a white-ish layer of waxy oils and cells that coats babies’ skin when they’re born.

But even though we don’t know exactly what causes this scent, scientists want to understand why it exists.

A 2013 study published in the journal Frontiers in Psychology found evidence that suggests this scent may affect certain brain regions of all women, but especially new mothers.

To test this, they rounded up a group of 30 women that were about the same age: 15 who had given birth within the previous six weeks, and 15 who had never given birth.

The researchers isolated baby smell from baby pajamas, specifically, from 18 newborns that weren’t related to any of the participants.

Then they had the women smell the newborn odors while undergoing brain scans.

All of the women showed activity in the reward-related areas of the brain.

There was slightly more brain activity in new moms.

Basically, the researchers think that the smell might act as a sort of incentive: to get the new moms to feel pleasure when they take care of babies.

This could promote more maternal care, and offset some of the exhaustion and hard work of parenting.

But what about new dads? Are they affected by this baby smell too?

Well, we still have a lot to learn about the smell of newborn babies.