Question

When technological advancement was necessary before scientists could begin to observe cells

Answer 1

Cells are the tiniest structural and functional unit of a living organism. They consist of nucleus and cytoplasm that are enclosed in a membrane. The cells are invisible to the naked eye and hence a microscope was needed to observe them. Robert Hooke was the first scientist to observe them under the microscope.

Answer 2

Oh boy. I think it was the microscope or the earlier version of that.