Any good design favors simplicity. Modern design follows the systematic use of only a few options for each visual attribute. There is no reason to use multiple font-families when one will do. There is no reason to use a plethora of colors when a small palette of 3 or 4 will suffice. There is no reason to vary between more than a pair of font-sizes or line widths. Strip away everything that is not essential and you will find the base of good design. There are many individuals responsible for birthing these design principles, either through art or necessity, but one of the most interesting and often underrepresented fathers of modern design is Herbert Bayer.
According to an article on Wikipedia, in an effort to replace the imperialistic government of Germany in 1919, the Weimar Republic was formed as a semi-presidential representative democracy. To afford the costs of World War I, Germany decided to fund the war through borrowing--not allowing an ounce of its currency to be converted to gold. As a result, the government began to buy foreign currency and significantly decreased the value of its Mark. From 1921 to 1924, Germany suffered a three-year period of hyperinflation. During this time, emergency banknotes were issued by Die Landesregierung Thüringen and designed by Bayer.
These banknotes embraced a simple and bold style now found in contemporary graphic design. Departing from the traditional bank note standard of serif fonts, swirls, and national symbols, Bayer's design featured grids, geometry, and sans-serif. This deviation from the norm was one of the first uses of modern design in the realm of politics and economics.
Despite their beauty, the insertion of Bayer's emergency currency into the economy did little to assuage inflation. Paper money was so worthless that it was burned as fuel. Herbert Bayer's banknotes provided heat for many.
Following the design of this currency, Bayer later created the "Universal" typeface which resonates with the widely-used sans-serif font today. The introduction of this typeface featured no uppercase letters, as Bayer believed people did not speak in upper- and lowercase. The simple beauty of his design allowed for greater innovations in effective communication.
Unlike many great artists and designers, Bayer spent the remainder of his career in advertising. The modernism he developed in Europe well served his innovative marketing in corporate America. The bold simplicity and geometrically balanced style was widely accepted. The principles of good design gave his work a universal appeal. As a result, much of his style permeates design today.