Reap

Reap[expr] gives the value of expr together with all expressions to which Sow has been applied during its evaluation. Expressions sown using Sow[e] or Sow[e,tagi] with different tags are given in different lists. 

Reap[expr,patt] reaps only expressions sown with tags that match patt. 

Reap[expr,{patt1,patt2,…}] puts expressions associated with each of the patti in a separate list. 

Reap[expr,patt,f] returns {expr,{f[tag1,{e11,e12,…}],…}}. 

Please visit the official Wolfram Language Reference for more details and examples on core symbols.