The movement of fluids, and in a way, the start of circulation and digestion, evolved in single celled prokaryotes right after LUCA to distribute nutrients and remove waste. Eventually, as eukaryotic cells grew larger and more complex, simple diffusion was no longer sufficient to move materials efficiently inside the cell. Cytoplasmic streaming and cytoskeleton-guided transport evolved to distribute nutrients, organelles, and waste within large single cells and simple multicellular colonies. This internal flow within a cell predates true circulatory and digestive systems: a trait of complex animals that evolve hundreds of millions of years later.