An essay -- and an assay -- of the current boom-baby, science fiction, analyzes its types and how they were developed, the scientific sources, and the potentials. An addict for years, the author has grown up with, and in, this medium, comments on the ideas and inventions, the good and the bad, SF uses in moving pictures, radio, TV and comics (very low levels here); Indicates the emotional and mythic qualities, and dignifies this popular reading with his findings. A worthwhile pruning shapes SF to higher standards and requirements.