Calcium oxalate is a chemical compound formed from calcium and oxalic acid. It appears as a white, crystalline substance and is commonly found in various plants, including spinach and rhubarb. In nature, it plays a role in the regulation of calcium levels in plants and can contribute to the formation of kidney stones in humans when present in high concentrations. In the human body, calcium oxalate can crystallize in the kidneys, leading to potential health issues. It is important to maintain a balanced diet to manage oxalate intake, as excessive consumption of high-oxalate foods may increase the risk of kidney stone formation.