You would measure that in grams, or milligrams.
gram
The answer depends on what characteristic you wish to measure: its mass, length, volume etc.
It depends on what you mean by size: its length, volume, surface area or even its mass.
You should clarify what you want to measure about it: its diameter, mass, weight, color, etc. If you want to measure its diameter, that would usually be specified in microns (= micrometers).
You would use kilograms (kg) to measure someone's mass in metric units.
You would use the metric unit "kilograms" to measure the mass of a wardrobe.
GRAMS
Tonnes
You would use grams (g) to measure a flower's mass.
Mass is measured using kilograms.
Mass is measured in kilograms.
Mass is measured in kilograms.
You would typically measure the mass of a snowflake in the metric unit of milligrams (mg), as snowflakes are very small and light objects.
The metric unit used to measure the mass of a pencil would be grams (g).
The tonne.
Kilograms