These two made the first successful microscope and helped with Hooke's research. They also figured out differently ways to grind glass to make it to magnify things.
Hooke discovered plant cells and found cell walls in thin cork slices. He also named what he found cells because the pores of the cork looked like what a monk compartment they lived in.
Contributed to cell theory by believing that there were seeds or eggs too small to see by the eye being planted into food, and other things. He tested this by using meat and flies.
Anton van Leeuwenhoek
He built the first "practical microscope" and described yeast, bacteria, and various other organisms underneath the microscope. Leeuwenhoek reported finding living and non-living organisms.
Found that parts of a plant organisms have cells. Schleiden also found the importance of the nucleus in the cell and had a sense that it had a connection to cell division.
His contribution was that he developed a cell theory for animals. Also elucidated further on Schleiden's theory and created the cell theory that everything is made of cells.
Came up with the idea that cells originate from other pre-existing cells. His idea wasn't completely original, but he better explained it in his publishings.
Found microorganisms were causing fermentation and diseases. From this he later experimented with boiling beef broth and showed the one that was exposed and the one that wasn't. The one that was exposed to air was shown as microbial contamination. This disproved spontaneous generation.