Q. In 1665 Robert Hooke, an English scientist, published his book Micrographia, in which he explained that pieces of cork viewed under the microscope presented small cavities similar to pores which were filled with air. On the basis of later knowledge, of what were the walls of those cavities constituted? What is the historical significance of that observation?

The walls of the cavities observed by Hooke were the walls of the plant cells that form the tissue. The observation led to the finding of the cells, a fact only possible after the invention of the microscope. In that work, Hooke established the term "cell", now extensively used in Biology, to designate those cavities seen under the microscope.