void grid3()
{

   TCanvas *c1 = new TCanvas("c1","Visualizzazione",10,10,1000,500);
   gStyle->SetOptStat(0);

   TH2C *h100 = new TH2C("h100","Visualizzazione",32,0.,32.,64,0.,64.);

   for (int i=0; i<64; i++) h100->Fill(25,i,1);

   h100->GetXaxis()->SetNdivisions(32);
   h100->GetYaxis()->SetNdivisions(16);
   h100->SetFillColor(3);
   h100->Draw("BOX");

   DrawGrid();
}

void DrawGrid()
{
   TPad *grid = new TPad("grid","",0,0,1,1);
   grid->Draw();
   grid->cd();
   grid->SetGrid();
   grid->SetFillStyle(4000);
      grid->SetFrameFillStyle(0);


   TH2 *hgrid = new TH2C("hgrid","",32,0.,32.,64,0.,64.);
   hgrid->Draw();
   hgrid->GetXaxis()->SetNdivisions(32);
   hgrid->GetYaxis()->SetNdivisions(64);
   hgrid->GetYaxis()->SetLabelOffset(999.);
   hgrid->GetXaxis()->SetLabelOffset(999.);
}