Q.Name the proposer(s) of cell theory.

Think of how a big idea in science rarely arrives fully formed in one person's head — it is usually stitched together by several people, each adding the piece they could see from where they stood. The cell theory is exactly this kind of stitched-together idea, and its history is really a story of four scientists handing the baton to one another.

The first big leap came from studying plants. A botanist named Matthias Schleiden, working in 1838, looked at a great many plants and concluded that they are all built from different kinds of cells, and that these cells are what make up the plant's tissues. A year later, in 1839, a zoologist named Theodore Schwann did the parallel job for animals. Examining many kinds of animal cells, he noticed that each cell is wrapped in a thin outer layer — the structure we now call the plasma membrane — and he also recognised that a cell wall is a special extra feature belonging only to plant cells. From all this he proposed that the bodies of both animals and plants are made of cells and the products of cells. …