The jalapeño is a medium-sized chili pepper pod type cultivar of the species Capsicum annuum. A mature jalapeño chili is 5–10 cm long and hangs down with a round, firm, smooth flesh of 25–38 mm wide.
Jalapeños are rich in vitamins A and C and potassium. They also have carotene -- an antioxidant that may help fight damage to your cells – as well as folate, vitamin K, and B vitamins. Many of their health benefits come from a compound called capsaicin. That's what makes the peppers spicy.