The prefix macr- or macro- means "large" or "long."
The prefix micr- or micro- means "small" or "tiny."
Examples: macroeconomics--the study of economic systems.
microeconomics--the study of a specific transaction or market.
The prefix micr- or micro- in the metric system means "millionth," so a microliter is a millionth of a liter. For more on this see Abbreviations of Measurements.