Paneth cells are specialized pyramidal secretory epithelial cells situated strictly at the base of the Crypts of Lieberkühn within the Small intestine (particularly dense in the ileum).
They contain prominent apical eosinophilic granules packed with antimicrobial peptides ($\alpha$-defensins, cryptdins, lysozyme, and secretory phospholipase $A_2$) that maintain intestinal microbiome homeostasis and mucosal barrier integrity.