The phrase "tiny organelles" refers to very small structures inside cells that help them perform specific functions, kind of like tiny machines. Full definition
It seems that the fertilizer increased the number of ribosomes (tiny organelles in the non-nuclear part of the cell). (religion-online.org)
The mitochondria are tiny organelles within our cells that are involved in using fuel to make energy to power the cells. (mindbodygreen.com)
There are tiny organelles within the cells called mitochondria which are the cell's «energy factories» and produce ATP, the cell's main energy source. (fitnessandpower.com)