itty bitty
Extremely small; tiny. Come on, Catherine, just try an itty bitty bite—if you don't like it, you don't have to eat the rest. You're scared of the neighbor's dog? But he's so itty bitty—he couldn't hurt you if you let him!
itty-bitty
Very small or petite; tiny. May I have an itty-bitty bite of your salmon? I just want a taste of it. How can you be afraid of such an itty-bitty spider?