The placenta. In the aftermath of giving birth, you might not spare much thought for it and your midwife may whisk it away before you clap eyes on the thing.
But, it's been feeding your little one nutrients and oxygen for 9 months – and some babies even appear to 'hug' theirs in ultrasound scans. So there's no denying it's a pretty wonderful thing.
We've heard lots about placenta pills from celeb mums such as Kim and Kourtney Kardashian and January Jones), plus more radically a placenta teddy bear, placenta photo frames and placenta anti-ageing serum.
But now Facebook and Instagram are being used to share something much more primal.
In New Zealand, it's a Maori tradition to return a baby's placenta to the land. Indeed the Maori's use the same word, whenua to mean land and placenta.
By burying the placenta and umbilical cord in the soil, sometimes under a tree, parents cement their baby's link to mother earth.
And now they've started sharing pictures celebrating this tradition.
The above photo shows a newborn Maori baby called Harper still connected to his placenta with the umbilical cord styled into the word 'love'.
Explaining the tradition on Facebook, photographer Emma Jean said: "Welcome earthside sweet little Harper.
"As a Maori baby his placenta will now be returned to the land.
"The word 'whenua' relates to the placenta and to the land. Whenua (placenta) is returned to the whenua (land) with the pito (umbilical cord) the link between the newborn and papatuanuku (mother earth). With this affinity established, each individual fulfils the role of curator, for papatuanuku (mother earth), which remains life long."
Other mothers have also shared their own placenta burial pictures and traditions, sometimes featuring their children next to the tree that's growing above their placenta.
Sharing a picture of her daughter's birth tree on Instagram (above), Sezah Flood wrote: "Somewhere in the depths of my Instagram timeline I posted a pic of my daughter sitting in front of her whenua or birthtree after we had just planted it..."
"133 weeks later here she is asking me to take a pic as she is super excited to see it working, as in the flowers have started to bloom."
Another mum, Lindsay Ray shared her photos on Instagram. "Thank you for watering me with love, feeding me with encouragement, & nourishing me with time & energy. I am growing beautiful because of you} From Birth to Earth ? Happy Mother's Day to all you amazing Mummas out there!"
Meanwhile, Amanda Earthchild buried her placenta in a pot (below). "Finally planted our baby's whenua (placenta) beneath this beautiful rhododendron, chosen by Papatuanuku herself. Now sitting at her Nannan and Kokos whare in Wanganui ? This weekend has been made of love and wonderful memories. Forever thankful ?," she wrote on Instagram.