This film is our cinematographic study of the life cycle of True Slime Molds (myxomycetes) by means of time-lapse microscopic shooting on 16mm film. In the woods at the rainy season, one can find small fruit bodies of various shapes and colors of true Slime Molds on the surface of decayed leaves and fallen trees. The myxoamoebae fusion takes place between compatible mating types. A gigantic amoebas-like cell containing numerous nuclei is called plasmodium. The plasmodium voraciously eats nearby myxoamoebae and grows larger through repeated fusion with diploid cells. The protoplasm of the growing plasmodium begins to flow to and fro. Within the protoplasmic streaming, several hundreds of mitochondria continue to supply energy source. By DAPI staining, we can see the DNA of the mitochondria of a living plasmodium. This is the first motion picture image taken of it. The formation of fruit bodies takes place in comparatively bright and dry spots. The plasmodium differentiates into numerous spores. True Slime Molds appeared on earth over a billion years ago. The energetic rhythm produced by the countless mitochondria holds the key to the mystery of evolution.