The Fundamental Unit of Life — Science STD 9 — Question

1. Cell walls.

Explanation:

Robert Hook discovered cells in 1655 with the help of compound microscope. He was observing insects, sand, bird feathers, fossils and plants. Once he was observing a thin slice of cork under the microscope he found a framework similar to honeycomb-like structure. He named those structures as cells but those were actually non living cell walls.