Sunspots appear dark (in visible light) because they are much cooler than the rest of the surface of the Sun. However, even though they appear dark, they are still very hot.
Answer:
Stem cells are cells with the potential to develop into many different types of cells in the body. They serve as a repair system for the body. There are two main types of stem cells: embryonic stem cells and adult stem cells
Explanation:
Totipotent (or Omnipotent) Stem Cells.
Pluripotent Stem Cells.
Multipotent Stem Cells.
Oligopotent Stem Cells.
Unipotent Stem Cells.
Glucose and amino acids move in and out of cells via facilitated diffusion.<span />
The solid inner core is made of mainly iron crystals with small amounts of nickel and heavier elements such as gold and platinum. The liquid outer core is a nickel iron alloy with small amounts of heavier elements.
