Which invention played the biggest role in the discovery of cells by early scientists?

compound microscope

Explanation:

Typically, a compound microscope is used for viewing samples at high magnification (40 - 1000x), which is achieved by the combined effect of two sets of lenses: the ocular lens (in the eyepiece) and the objective lenses (close to the sample). ... Objective. Focus wheel to move the stage.

The correct answer is high levels of radiation.

On April  26,1986 a nuclear reactor system got destroyed in the nuclear power station at Chernobyl in Ukraine.

The accident was followed by fire and massive release of radioactive waste material in the environment.

Boron and sand was used to stop the fire and radioactive release from further spreading.