Well Cell Theory states that all organisms are composed of one or more cells,the cell is the basic unit of structure and function, and all cells come from preexisting cells.
It all started back when Matthias Schleiden found that all plants are made of cells. Theodor Schwann then found that all animals were made of cells and together they created the concept of Cell Theory.
Well what about the part where its says that cells come from preexisting cells?
That was added into the theory later Rudolf Virchow had settled the argument between Schwann and Schleiden as one of them agreed with Vrichow and the other said cells form spontaneously.
Where did the term cell come from anyway?
Robert Hooke coined the term cell as he thought they looked like the chambers that monks lived in in the monasteries.
Is there anything else I should know?
Robert Brown discovered the nucleus of a cell. Which is pretty important.