What is the best microscope to use to examine the one-cell organisms in pond water

How can scientists test their ideas about the origin of the universe if they can't physically interact with or study?

An organ system consists of a group of organs that performs specific functions necessary for the survival of an organism. humans have eleven different organ systems: integumentary, skeletal, muscular, nervous, endocrine, circulatory, lymphatic, respiratory, digestive, urinary, and reproductive. discuss the function of neurons, the brain and the spinal cord within the human nervous system while explaining the interrelationship of each organ.

What terms describes being out of water after being submerged