Question

what the contribution of Robert hooke,Leewenhoek, Robert brown​

Answer 1

Robert Hooke was the first scientist to observe cells,in 1665. He observed the cells in a cork slice with the help of a primitive microscope.

 Robert Brown: Robert Brown in 1831 who discovered the nucleus in the cell.

Van Leeuwenhoek discovered "protozoa" - the single-celled organisms and he called them "animalcules". He also improved the microscope and laid foundation for microbiology. He is often cited as the first microbiologist to study muscle fibers,bacteria, spermatozoa and blood flow in capillaries.