"Think of oil and water. They don't mix. The phosphate "head" is like water and the lipid "tails" are the oil. You learn in chemistry that polar substances will dissolve polar substances and apolar dissolve apolar. If you mix apolar and polar, they just separate."
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.