With the arrival of the 20th century, significant investments were made to enlarge the factory and to modernize equipment and production techniques. This was the golden age of skimmers and straw hats in general, with great emphasis on the use of Italian and Oriental plaits. The market was growing and this meant that successful businesses had to anticipate the clientele's demand for novelty and innovation. To meet this demand Tesi introduced new styles and a new material: panama.

During these years, Tesi confirmed its international prestige and established solid commercial contacts with Central and North America for the supply of raw materials.

After the Second World War the business continued to occupy a dominant position, although hats in general were no longer considered an indispensable element of clothing. With the post-war boom, habits and life-styles were changing as the rhythms became frenetic. Hats were still viewed as an important expression of fashion trends, but the classic straws entered a decline which reached its worse during the late 60's.

A solid international reputation and the ability to renew and vary production enabled the company to surmount these difficulties by introducing new lines of cloth and felt hats.

Today experience is the keystone of company success, as the fifth generation carries on the Tesi family tradition of excellence and renown.

Tesi contributed to the foundation of the straw museum, located in the town of Signa near Florence: Museo della Paglia Domenico Michelacci.