What is the fundamental unit of life? Who discovered it? How can they be observed?

(N/A) $(i)$ The fundamental unit of life is the cell.
$(ii)$ The cell was first discovered by Robert Hooke in $1665$.
$(iii)$ Cells are generally observed under a microscope because they are microscopic in size. However, some cells are large enough to be seen with the naked eye, for example, an ostrich egg.