diff --git a/hw3-heat-fft/fft.hh b/hw3-heat-fft/fft.hh
index 0319abe1..a1b74179 100644
--- a/hw3-heat-fft/fft.hh
+++ b/hw3-heat-fft/fft.hh
@@ -1,37 +1,86 @@
 #ifndef FFT_HH
 #define FFT_HH
 /* ------------------------------------------------------ */
 #include "matrix.hh"
 #include "my_types.hh"
 #include <fftw3.h>
 /* ------------------------------------------------------ */
 
 struct FFT {
 
   static Matrix<complex> transform(Matrix<complex>& m);
   static Matrix<complex> itransform(Matrix<complex>& m);
 
   static Matrix<std::complex<int>> computeFrequencies(int size);
 
 };
 
 /* ------------------------------------------------------ */
 
 inline Matrix<complex> FFT::transform(Matrix<complex>& m_in) {
+    int N = m_in.rows();
+
+    std::cout << "N = " << N << std::endl;
+
+    // Declare/initialize in and out for FFTW
+    std::vector<complex>  in(N*N);
+    std::vector<complex> out(N*N);
+
+    fftw_plan plan = fftw_plan_dft_2d( N,
+                                       N,
+                                       reinterpret_cast<fftw_complex*>(&in[0]),
+                                       reinterpret_cast<fftw_complex*>(&out[0]),
+                                       FFTW_FORWARD,
+                                       FFTW_ESTIMATE );
+
+    // Fill "in" with input-matrix values
+    for (auto&& entry : index(m_in)) {
+
+        // Get i and j index of matrix entry
+        int i = std::get<0>(entry);
+        int j = std::get<1>(entry);
+
+        // Value of matrix entry at (i,j)
+        complex val = std::get<2>(entry);
+
+        // Create 1D index k from 2D indices (i,j)
+        int k = i + j * N;
+
+        // Insert value into in
+        in[k] = val;
+    }
+
+    // Execute FFTW
+    fftw_execute(plan);
+
+    // Fill output-matrix with "out"-values
+    Matrix<complex> m_out(N);
+    for (auto&& entry : index(m_out)) {
+      int i = std::get<0>(entry);
+      int j = std::get<1>(entry);
+      complex& v = std::get<2>(entry);
+      int k = i + j * N;
+      v = out[k];
+    }
+
+    // Destroy FFTW
+    fftw_destroy_plan(plan);
+
+    return m_out;
 }
 
 /* ------------------------------------------------------ */
 
 inline Matrix<complex> FFT::itransform(Matrix<complex>& m_in) {
 }
 
 /* ------------------------------------------------------ */
 
 
 /* ------------------------------------------------------ */
 
 inline Matrix<std::complex<int>> FFT::computeFrequencies(int size) {
 
 }
 
 #endif  // FFT_HH