Answer:
Millimeter and meter
Step-by-step explanation:
Cellphones are only a few millimeters in thickness.
It is easier to say 5 millimeter than 0.0005 meter.
The unit we use must help others easily visualize and understand the size of the object.
a 5 millimeter is easy to visualize than a 0.0005 meter or a 5,000,000 nano meter
In the same way, a tree in our backyard usually grow as tall as a few meters. ( remember trees in amazon forest might grow as tall as a few kilometers). so in the case of trees in our home the right unit to measure them is meters.