Spore
noun, の adjective
The child of a cell is a spore. They're just as tiny and they're floating all around you right now.
ほうし
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
キノコの胞子はとても小さいので、肉眼で形は分かりません。
Because mushroom spores are so small, their appearance can’t be understood with the naked eye.