Cell theory was given by Matthias Schleiden and Theodor Schwann in 1839 which states that all the living things on the planet earth is composed of cells and these cells are the smallest, basic and functional unit of life.
Cell theory also states that a preexisting cell is responsible for the production of new cell which was early thought that new cells comes from non- living matters.
Therefore cell theory proved that new cells come from other cells that are already existing in the world. In eukaryotes, cells divide by the process of mitosis and meiosis and in prokaryotes like bacteria cell divide through binary fission and give rise to new cells.
Asteroids vary greatly in size and are mostly made up of frozen water and gas. This one is true.
They are said to be "mostly formed of ice and gas" as they rarely can be found consisting of stone, nickel and iron. These are extremely dangerous in our Universe.
