gganimate plot not showing and saving bunch of .png's

I am trying to replicate a simple example about gganimate from here. The problem is simple ggplot part works fine but when I add transition_statesrstudio starts rendering and then saves bunch of gganim_plotXXXX.png files and doesn't show the expected animation.

First question is obviously: Am I doing something wrong so that animation doesn't work?

Second question is: Is saving bunch of .png files standard for gganimate?

Thanks in advance

library(gganimate)

p <- ggplot(iris, aes(x = Petal.Width, y = Petal.Length)) + 
         geom_point()

anim <- p + 
  transition_states(Species,
                    transition_length = 2,
                    state_length = 1)
anim