Across
1
Group of similar cells
5
Center of an atom or cell
6
Nerve cell in the brain
8
Magnetic metallic element
Down
2
Biological catalyst
3
Icy body with a tail near the sun
4
Measure of matter in an object
7
Amplified beam of light
9
Naturally occurring inorganic solid
10
Substance with pH below 7
11
Blocking of light by a celestial body
12
Unit of energy