During this check point chromosomes become invisible

interphase

Explanation:

it's the resting stage of cell where the chromosome is not seen under the light microscope.

brain development. a child's brain undergoes an amazing period of development from birth to three—producing more than a million neural connections each second. the development of the brain is influenced by many factors, including a child's relationships, experiences and environment.

explanation:

condenser is used to focus in the light microscope.