A smash cake is a small cake made specifically for a babys first birthday celebration. It is called a "smash" cake because the baby is encouraged to dig in and make a mess by using their hands to enjoy the cake. The cake is meant to be messy and fun, and it is typically used as a prop for a first birthday photoshoot. The cake is usually smaller in size, about four to six inches in diameter and one to three tiers, and is meant to be devoured or destroyed by the baby. It is a fun and adorable way to celebrate a babys first birthday and capture memorable moments.