We are looking at a juvenile Mesodon thyroidus, a common land snail snail of northeast North America. Unlike the shells of old adults, its was still thin and translucent. So the flash shining from underneath revealed its organs.
The yellow arrow is pointing at the snail's lung, specifically, at the primary pulmonary vein. The long tube curving around the spire of the snail's shell, marked by the orange arrow, is the rectum at the end of the snail's digestive system. The dark matter filling it towards the back is feces on their way out. The white arrow is highlighting a red organ. Frankly, I am not sure of its identity. It could be the albumen gland or the ovotestis or a part of the digestive gland. When I get a chance, I will compare its position with those of the organs of some preserved Mesodon and come up with a more definite name for it.
Here is a previous post about another backlit snail.