When Alexandra Bolen was pregnant earlier this year, she connected online with other moms, several of whom were pregnant after suffering a loss during a previous pregnancy. That's when Bolen first heard the term "rainbow baby," and it's when she decided to use her skills as a photographer to pay tribute to these mothers and help them share their stories.

So what is a rainbow baby? A rainbow baby is a child born to a mother who has suffered a miscarriage or stillbirth in a previous pregnancy. For many grieving mothers, this baby is the light that comes after the tragedy of losing a baby — just like a rainbow.

Bolen recruited six of these mothers to help her with her photographic tribute to rainbow babies and their mothers.

"I was all kinds of nervous," Bolen told her local NBC affiliate, "In my gut I wanted to nail this. Not just for my creative heart but for these moms, for their beautiful angels in heaven."

Bolen's photo (pictured above,) features six mothers of rainbow babies, some of them still pregnant, against a backdrop of rainbow-hued smoke bombs. After sharing it on Facebook on her Shutter Darling Photography Studio page, the pic went viral with tens of thousands of likes, shares and comments.

Here's the prose she included with her picture:

"A rainbow is a promise

of sunshine after rain

of calm after storms

of joy after sadness

of peace after pain

of love after loss."

Bolen's viral photo is one of many that have been posted on social media sites in recent years to call attention to the mothers who have suffered from a loss during pregnancy and the courage and commitment it takes for those mothers to keep trying for a new baby while still grieving the babies they will never meet.

This image, by photographer Jen Priester, is of rainbow baby Charlotte, whose mom Cathy Matthews suffered a miscarriage a few months before becoming pregnant with Charlotte.

And this photo, captured by photographer JoAnn Marrero, features Jessica Mahoney, a mother pregnant with her rainbow baby after suffering six miscarriages.

"Six babies lost to have the honor to carry this rainbow baby," Mahoney wrote in a caption accompanying the phone, "I hope my story helps someone else to know they are not alone, as the journey of loss and infertility is dark and lonely."