Audrey Sillick's article, first printed in 1988, provides a theory base for Maria Montessori's foundational emphasis on the biological sciences and the sustainability of a living, organic planet Earth as part of the educational process "of becoming more fully human." Ms. Sillick helps link primary-level biology with the special energy and cohesion of the Montessori view of Cosmic Education, the particular engagement of the senses that nature elicits, along with a celebration of the child's interactive process with nature, which, in fact, is our hope for the future. [This article is reprinted from "The NAMTA Journal" 13,2 (1988, Spring): 27-32.]