Why is most life symmetrical externally but not Internally?

Most living things look the same on both sides but have different insides because they grow that way.

Imagine you're building a house. You start with a symmetrical base, like two equal walls, one on each side of the front door. That’s easy and makes sense. But once you go inside, things get more complicated. Maybe you put the kitchen on one side and the living room on the other. Or maybe your bedroom is bigger than your friend's. It doesn’t have to be the same on both sides, it just needs to work well.

Think of a sandwich: you start with two slices of bread, which are symmetrical outside. But inside? Maybe you put more cheese on one side or add a pickle only on one half. It still tastes good, it just isn’t perfectly balanced inside.

That’s like most living things! They grow from the outside in, and they start with symmetry, but as they grow, their insides can be different, just like your sandwich or your house.