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You might want to grab a box of tissues before this one...

A touching video shows a mother learning that her dying daughter's preschool teacher will donate a kidney to the little girl.

Dena Carreyn, of Madison, Wisconsin, found out last year that her four-year-old daughter, Lyla, has a rare autoimmune-related vasculitis known as Microscopic Polyangiitis (or MPA), which causes damaging kidney failure.

When it became clear that Lyla would need a new kidney, her family started a nationwide donor search this summer.

Earlier this month, Dena received the amazing news that Lyla's preschool teacher, Beth Battista, was a perfect match, and would be donating her kidney.

Dena posted the emotional video on Facebook, showing her being given a box by Battista and other school staff.

When she opens it, she sees a note that reads: "I may just be her teacher now, but soon a little piece of me will be with Lyla forever. I'm Lyla's kidney donor."

The mother and teacher share an emotional embrace after the big news is revealed.

"Many people think teachers are heroes," Dena wrote on Facebook. "Beth Battista is more than our hero; she is our miracle."

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