The Sejm, until 1573 summoned by the king at his discretion (for example when he needed funds to wage a war), composed of the two chambers presided over by the monarch, became in the course of the 16th century the main organ of the state power.
Seim, mida aastani 1573 kutsuti kokku kuninga äranägemisel (näiteks, kui ta vajas raha sõjapidamiseks), mis koosnes kahest kojast, mille eesistujaks monarh, sai 16. sajandi jooksul peamiseks riigivõimu organiks.