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.
The nucleus is separated from the cytoplasm by a membrane called a nuclear envelope.This helps to protect the cell's chromosomes which is where the DNA is located.The nucleus was first discovered by microscopist Antonie van Leeuwenhoek in the mid-1600s while he was examining the red blood cells of salmon.