Microtext printing is a super small set of print that is very difficult to see with the naked eye. Most persons need a good magnifying glass to be able to view the microtext, and even then it can be difficult. I have had to break out my 16X Jewelers Loupe to be able to read the smallest text I've found. Microtext on banknotes is an ever evolving method of an anti-counterfeiting technique that makes printing banknotes on copiers or computer printers an impossible task. The microtext is so small that even the latest computers have extreme difficulty in reaching a quality of print that comes close to the real thing. For those who know what to look for, the areas of micotext on counterfeit notes is typically blurred or reduced to a simple line. The banknote printers have an advantage over the easy to use printer and copiers in that their time and effort in making the printing plates is much more detailed and can be printed almost endlessly with the same quality.
It is difficult to say when microtext was actually incorporated into banknotes because there has been a long evolution of its use from being placed in the under-print of older banknotes to today's incorporation into various design elements on banknotes, growing ever smaller as technology allows.
Below are a few examples of micropint that can be found on banknotes. The microprint, along with many other security features are what keeps our money safe from counterfeiters and helps immeasurably in maintaining it's value.