In a search for clues about size, the documentary shows why the sun and planets are so large, why insects have shrunk in the course of evolution and how tall trees can actually grow. Fantastic thought experiments are visualized: animals grow many times their normal size and a man is shrunk to the size of an insect. The results of the unnatural reversal of size ratios have incredible consequences. What are the advantages and disadvantages? "Size matters" is a scientific documentary narrated with fictional scenes. Parallel worlds are created in which size appears in a completely new light, often in a different way than previously known. Modern, astonishing CGI sequences support internationally recognized scientists on a journey to both ends of the size scale and help to understand the world in its dimensions.