Which scientist observed and described living cells for the first time?

What could the cell theory proposed by Schleiden and Schwann not explain?

The cell theory was proposed by $T. Schwann$. Who else proposed the cell theory?

Select the statements which are related to Schwann.
$(i)$ He reported that cells have a thin outer layer which is today known as plasma membrane.
$(ii)$ Cell wall is a unique character of the plant cell.
$(iii)$ Body of plants and animals are composed of cells and products of cells.

Who proposed the statement '$Omnis cellula-e cellula$'?

What is typically used to study the structure of a plant cell?