A snail's shell is its permanent home -- but how do these wee, soft, slimy creatures grow hard, beautiful shells? Learn how it works in this episode of BrainStuff.Learn more about advertising on the HowStuffWorks podcasts at www.howstuffworks.com/advertisers.htmAnd to learn about your ad choices when listening to podcasts, visit https://www.howstuffworks.com/privacy.htm#ad-choices
