Vikings under the chief Rollo were given permission by the Frankish king to settle in the territory we call Normandy. They became a duchy of West Francia. Most of the Vikings were men, so they took native brides and overtime mixed with French nobility and commoners as well. The Norse heavily settle the land around Cherborg and Caen.

https://en.wikipedia.org/wiki/Normans#Settling_of_Normandy

They then embarked on one of the most incredible expansions in history. Setting out from this tiny duchy, Norman warlords conquered England, Sicily and all of southern Italy. They even set up a polity in the Levant.

However, by the 13th century they lost their unique character and became generic Frenchmen. Their adventurous nature was a product of Norse adventurism and their lack of land or wealth. By that time they had become rich and Norman adventurers had carved out many fiefdoms across Europe.

I feel sad when I read about the exploits and unbelievable feats of the Norse people during the Viking age, Norman conquests and later Swedish Empire. It beggars belief that present day Swedes and Danes are descended from those men.