How did grenades effect WW1?

grenades were used long before the first world war, The original grenades looked like pomegranates so that's where the name came from. and the original soldiers who used them were called grenadiers.

they were being used in the18th century but I don't know if there were any before then. I would say machine guns changed the first world war more then grenades.

It made trench warfare more Intense and more nastier than it already was with bayonets and all that.