Robert Hooke did research that contributed to the Cell Theory. He actually coined the term "cell" in his book "Micrographia", which was based on observations of cork. The dead plant cells looked like cells that monks lived in--rectangular boxes.
In the late 1600's he worked with a light microscope that he helped to design. It contained an eyepiece, a barrel, a focusing screw, an objective, a specimen holder and was accompanied by a light source from an oil lamp. This lamp gave off light which passed through a flask filled with water to help illuminate specimens he was observing.
Anton van Leeuwenhoek designed his own simple microscopes which were capable of between 70x and 250X magnification. He designed his own lenses which were of an excellent quality. Although not technically a scientist, he extensively studied the microscopic world and kept excellent records of his observations. His microscopes were considered to be superior to all other models of the time period.
The advent of the microscope changed the way the world was viewed at the time in terms of its living inhabitants. It opened up a new world invisible to the naked eye.
The links I have provided have pictures and details regarding each microscope.