Tillie's science teacher, Mr Goodman, has described the atoms in a way that makes Tillie regard them with awe. What did Mr Goodman tell her about atoms?
The opening act of The Effect of Gamma Rays on the Man-in-the-Moon Marigolds beings with Tillie's voice-over regarding Mr. Goodman's explanation of what atoms are. Tillie reproduces Mr. Goodman's explanation and the way in which he prompted her analysis. Tilly tells us that Mr. Goodman asks for her to look at her hand. Then, he explains how, in reality, every element that makes up our human composite is a fragment of an infinite Universe:
for a part of it came from a star that exploded too long ago to imagine. This part of me was formed from a tongue of fire that screamed through the heavens until there was our sun.
This is Mr. Goodman's way to explain that, essentially, we all have a common core. We are all made of stardust, meteor dust, and every other element that envelops our galaxy. This is the part of the explanation that makes Tillie, who possesses a very inquisitive mind, come to a higher realization that brings her to complete awe:
and this part of me–this tiny part of me — was on the Sun when it itself exploded and whirled in a great storm until the planets came to be.