The right shampoo can mean the difference between hair that stays bouncy beyond day three and strands that fall flat right after a blowout. According to chemical engineer and founder of Sister Scientist , Erica Douglas, an effective volumizing shampoo should have ingredients that enhance and preserve the natural thickness of your hair. "A good volumizing shampoo will usually contain proteins or amino acids to help replace what’s been stripped from the hair in daily styling," she tells Refinery29. "Picking the right one comes down to knowing the needs of your hair."