middle lamella
"The two cell walls are like slices of bread; the middle lamella is like a layer of peanut butter."
"The middle lamella is like an appetizer. It forms as the cell plate splitting an existing cell, one of the first steps in making the new cell wall, but is not yet complete on its own. Similarly, you eat an appetizer before a dinner, and it quenches your hunger a bit, but it's not a real meal."
A really good blog post comparing cell walls to food such as a layer cake and Mexican food.
METAMIA is a free database of analogy and metaphor. Anyone can contribute or search. The subject matter can be anything. Science is popular, but poetry is encouraged. The goal is to integrate our fluid muses with the stark literalism of a relational database. Metamia is like a girdle for your muses, a cognitive girdle.