Apple CEO Tim Cook reached out via Twitter to Aaron Levie after his cloud file-sharing company Box opened on the New York Stock Exchange this morning.

Box saw a 40 percent pop on its initial offering of $14 a share, arriving at $20.20 on the NYSE today. The company took the long road to get to its IPO. Box first filed an S-1 form in March 2014 and then twice delayed its NYSE debut.