Crack UNDER sapphire crystal?!?

Does anyone know what is between the sapphire and the OLED display on the Apple Watch 2 Stainless Steel version?

My watch fell onto our porcelain sink causing a crack under the sapphire. I'm curious what is actually cracked since the sapphire appears unscathed.

I found similiar complaints ********** but am unable to identify the specific material appearing cracked.