Answer:

1. Several scientists have made significant contributions to the development of microscopy throughout history. Some notable contributors include:

- Antonie van Leeuwenhoek: A Dutch scientist often referred to as the "Father of Microbiology," Leeuwenhoek is credited with perfecting the microscope in the 17th century. He was the first to observe and describe microorganisms, such as bacteria, using his handcrafted microscopes.

- Robert Hooke: An English scientist, Hooke is known for his work in microscopy during the 17th century. He published a book called "Micrographia" in 1665, where he described and illustrated various objects observed under a microscope, including cells and plant tissues.

- Ernst Abbe: A German physicist and mathematician, Abbe made significant advancements in optical theory during the late 19th century. He developed the concept of numerical aperture and formulated mathematical equations that improved the resolution of microscopes.

- Max Knoll and Ernst Ruska: These German scientists developed the first practical electron microscope in the early 1930s. Ernst Ruska, along with his student Max Knoll, built the prototype electron microscope, which allowed for higher resolution and magnification compared to traditional light microscopes.

2. The contributions of each scientist are as follows:

- Antonie van Leeuwenhoek: Leeuwenhoek's main contribution was the improvement and refinement of the microscope. He achieved much higher magnification and observed various microorganisms for the first time, providing crucial insights into the microscopic world.

- Robert Hooke: Hooke's major contribution was his book "Micrographia," which popularized the use of microscopes and brought attention to the microscopic details of various objects. He coined the term "cell" while observing cork tissue, which led to the development of cell theory.

- Ernst Abbe: Abbe's contributions were primarily in the field of optics. He developed theories and mathematical equations that improved the resolution and quality of microscope images. His work on numerical aperture and the Abbe diffraction limit played a crucial role in advancing microscopy.

- Max Knoll and Ernst Ruska: Knoll and Ruska's invention of the electron microscope revolutionized microscopy. Electron microscopes use beams of electrons instead of light to image specimens, allowing for much higher magnification and resolution. This development opened up new possibilities for studying the ultrastructure of cells and nanoscale materials.

3. These scientists are considered contributors to the development of microscopy because their work significantly advanced our understanding of the microscopic world and improved the capabilities of microscopes. They either developed new microscope designs, improved existing ones, or made groundbreaking discoveries using microscopy techniques. Their contributions paved the way for further advancements in the field and enabled scientists to explore and observe the intricate details of living organisms, cells, and materials at the micro and nanoscale.