{
   gROOT->Reset();
   TH3F *h3a = new TH3F("h3a","testa fitz",20,-4,4,20,-4,4,20,0,20);
   TH3F *h3b = new TH3F("h3b","testb fitz",20,-4,4,20,-4,4,20,0,20);
   for (Int_t i=0;i<10000;i++) {
      Float_t x = gRandom->Gaus(0,1);
      Float_t y = gRandom->Gaus(0,1);
      Float_t z = gRandom->Gaus(10,4);
      h3a->Fill(x,y,z);
   }
   for (Int_t i=0;i<1000;i++) {
      Float_t x = gRandom->Gaus(0,1);
      Float_t y = gRandom->Gaus(0,1);
      Float_t z = gRandom->Gaus(10,4);
      h3b->Fill(x,y,z);
   }
   h3a->SetMarkerColor(kBlue);
   h3b->SetMarkerColor(kRed);

   TCanvas *myCanvas = new TCanvas("myCanvas","Title",800, 600);
   myCanvas->SetRightMargin(0.5);
   myCanvas->cd();

   h3a->Draw("cont");      
   h3b->Draw("same");      
}