What are motor skills? You might hear about the development of fine and gross motor skills in the pediatricianâs office, parenting magazines or a baby development book. What exactly are they? This is actually a pretty complicated question.
The cell was first discovered by Robert Hooke in 1665 using a microscope. The first cell theory is credited to the work of Theodor Schwann and Matthias Jakob Schleiden in the 1830s. In this theory the internal contents of cells were called protoplasm and described as a jelly-like substance, sometimes called living jelly.
In 1838 Schwann became familiar with Matthias Schleiden's microscopic research on plants. Schleiden described plant cells and proposed a cell theory which he was certain was the key to plant anatomy and growth. Pursuing this line of research on animal tissues, Schwann not only verified the existence of cells, but he traced the development of many adult tissues from early embryo stages.