A dendroid is an arcwise connected continuum such that the intersection of any two of its subcontinua is connected. In 1985, Tadeusz Mackiowiak constructed a contractible non-selectible dendroid X. Through the years the originality of the structure of this dendroid has been useful to produce several counterexamples.

In this talk we will mention some other important properties of X and some of the examples that have constructed using it, including a new one related to the hyperspace of subcontinua with empty interior of a continuum.