diff --git a/pipeline/stage02_processing/README.md b/pipeline/stage02_processing/README.md
index 4c843118..3b131b1f 100644
--- a/pipeline/stage02_processing/README.md
+++ b/pipeline/stage02_processing/README.md
@@ -32,5 +32,6 @@ Other as in other stages, in this stage, all blocks are re-executed with every s
 |__normalization__|divides signals by factor|`NORMALIZE_BY`|
 |__roi_selection__|masks area of low signal intensity|`INTENSITY_THRESHOLD`|
 |__detrending__|removes (linear, quadratic, ..) trends in signals|`DETRENDING_ORDER`|
+|__hierarchical_spatial_sampling__|non homogeneous spatial smoothing according to macro pixels sigma to noise ratio|`EXIT_CONDITION`, `SIGNAL_EVALUATION_METHOD`, `N_BAD_NODES`, `VOTING_THRESHOLD`|
 
 (_plotting parameters in italic_)
diff --git a/pipeline/stage02_processing/Snakefile b/pipeline/stage02_processing/Snakefile
index cf4921a3..d10c7ca0 100644
--- a/pipeline/stage02_processing/Snakefile
+++ b/pipeline/stage02_processing/Snakefile
@@ -31,6 +31,11 @@ PLOT_FORMAT = config["PLOT_FORMAT"]
 
 MACRO_PIXEL_DIM = config["MACRO_PIXEL_DIM"]
 
+N_BAD_NODES = config["N_BAD_NODES"]
+VOTING_THRESHOLD = config["VOTING_THRESHOLD"]
+EXIT_CONDITION = config["EXIT_CONDITION"]
+SIGNAL_EVALUATION_METHOD = config["SIGNAL_EVALUATION_METHOD"]
+
 BLOCK_ORDER = config["BLOCK_ORDER"]
 NORMALIZE_BY = config["NORMALIZE_BY"]
 HIGHPASS_FREQ = config["HIGHPASS_FREQ"]
@@ -386,3 +391,31 @@ rule subsampling:
                               --output "{output.data}" \
                               --target_rate {params.target_rate}
         """
+
+rule hierarchical_spatial_sampling:
+    input:
+        is_clear = os.path.join('{dir}', 'clear.done'),
+        data = input_file,
+        script = os.path.join('scripts', 'hierarchical_spatial_sampling.py')
+    output:
+        data = os.path.join('{dir}', '{rule_name}',
+                            'hierarchical_spatial_sampling.'+NEO_FORMAT),
+        img = report(os.path.join('{dir}', '{rule_name}',
+                                  'hierarchical_spatial_sampling.'+PLOT_FORMAT))
+    params:
+        n_bad_nodes = N_BAD_NODES,
+        voting_threshold = VOTING_THRESHOLD,
+        exit_condition = EXIT_CONDITION,
+        signal_eval_method = SIGNAL_EVALUATION_METHOD,
+    shell:
+        """
+        {ADD_UTILS}
+        python {input.script} --data "{input.data}" \
+                              --output "{output.data}" \
+                              --output_img "{output.img}" \
+                              --n_bad_nodes {params.n_bad_nodes} \
+                              --voting_threshold {params.voting_threshold} \
+                              --exit_condition "{params.exit_condition}" \
+                              --signal_eval_method "{params.signal_eval_method}"
+
+        """
diff --git a/pipeline/stage02_processing/configs/config_template.yaml b/pipeline/stage02_processing/configs/config_template.yaml
index 278d4a50..bc0e1483 100644
--- a/pipeline/stage02_processing/configs/config_template.yaml
+++ b/pipeline/stage02_processing/configs/config_template.yaml
@@ -27,7 +27,7 @@ PLOT_FORMAT: 'png'
 # and in which order. Execution order is from first to last entry.
 # The available blocks are:
 # 'background_subtraction', 'frequency_filter', 'normalization', 'detrending',
-# 'spatial_downsampling', 'roi_selection', 'logMUA_estimation', 'phase_transform',
+# 'spatial_downsampling', 'hierarchical_spatial_sampling', 'roi_selection', 'logMUA_estimation', 'phase_transform',
 # 'zscore', 'subsampling'
 # Default: empty list [] -> it skips any processing blocks and returns the same
 # as input but, different from plot obtained from stage01, here the values on
@@ -42,6 +42,18 @@ BLOCK_ORDER: []
 #################################
 MACRO_PIXEL_DIM: 2
 
+# BLOCK - hierarchical_spatial_sampling 
+#################################
+# method to use for the exit mode: 'consecutive', 'voting', 'standard'
+EXIT_CONDITION: 'voting'
+# method to evaluate the signal to noise ration of a macro pixel
+SIGNAL_EVALUATION_METHOD: 'shapiro'
+# number of bad nodes in the same branch to meet the exit condition
+N_BAD_NODES: 2
+# only for "voting" method: threshold fraction of 
+# "bad children" to keep investigating the tree
+VOTING_THRESHOLD: 0.5
+
 # BLOCK - normalization
 #######################
 # Normalize the data (devide channels-wise) by either:
diff --git a/pipeline/stage02_processing/scripts/hierarchical_spatial_sampling.py b/pipeline/stage02_processing/scripts/hierarchical_spatial_sampling.py
new file mode 100644
index 00000000..79ded5da
--- /dev/null
+++ b/pipeline/stage02_processing/scripts/hierarchical_spatial_sampling.py
@@ -0,0 +1,218 @@
+import neo
+import numpy as np
+from scipy.stats import shapiro
+import matplotlib.pyplot as plt
+import argparse
+from utils.io import load_neo, write_neo, save_plot
+from utils.parse import none_or_float, none_or_int, none_or_str
+from utils.neo import analogsignals_to_imagesequences, imagesequences_to_analogsignals
+
+
+def next_power_of_2(n):
+    exponent = np.ceil(np.log2(n))
+    return int(2**exponent)
+
+def ComputeCenterOfMass(s, scale):
+    # compute the center of mass of a macropixel con nan values
+    mean = np.nanmean(s, axis = 2)
+    idx = np.where(~np.isnan(mean))
+    x_cm = (np.mean(idx[0])+0.5)*scale
+    y_cm = (np.mean(idx[1])+0.5)*scale
+    if np.isnan(x_cm): x_cm = np.shape(mean)[0]/2
+    if np.isnan(y_cm): y_cm = np.shape(mean)[1]/2
+    return(x_cm, y_cm)
+
+# List con x,y,L,flag,x_parent, y_parent, L_parent
+
+def CheckCondition(coords, Input_image, method = 'shapiro'):
+    #function to check whether node is compliant with the condition
+    value = np.nanmean(Input_image[coords[0]:coords[0]+coords[2], coords[1]:coords[1]+coords[2]], axis = (0,1))
+    if np.isnan(np.nanmax(value)):
+        return(1)
+    else:
+        if method == 'shapiro':
+            stat, p = shapiro(value)
+            if p <= 0.05:
+                return(0)
+            else:
+                return(1)
+
+def NewLayer(l, Input_image, evaluation_method):
+    new_list = []
+    # first leaf
+    cond = CheckCondition([l[0], l[1], l[2]//2], Input_image, evaluation_method)
+    new_list.append([l[0], l[1], l[2]//2, (l[3]+cond)*cond, l[0], l[1], l[2]])
+
+    # second leaf
+    cond = CheckCondition([l[0], l[1]+l[2]//2, l[2]//2], Input_image, evaluation_method)
+    new_list.append([l[0], l[1]+l[2]//2, l[2]//2, (l[3]+cond)*cond, l[0], l[1], l[2]])
+
+    # third leaf
+    cond = CheckCondition([l[0]+l[2]//2, l[1], l[2]//2], Input_image, evaluation_method)
+    new_list.append([l[0]+l[2]//2, l[1], l[2]//2, (l[3]+cond)*cond, l[0], l[1], l[2]])
+    
+    # fourth leaf
+    cond = CheckCondition([l[0]+l[2]//2, l[1]+l[2]//2, l[2]//2], Input_image, evaluation_method)
+    new_list.append([l[0]+l[2]//2, l[1]+l[2]//2, l[2]//2, (l[3]+cond)*cond, l[0], l[1], l[2]])
+    
+    return(new_list)
+
+def CreateMacroPixel(Input_image, exit_method = 'consecutive', signal_eval_method = 'shapiro', threshold = 0.5, n_bad = 2):
+    # initialized node list
+    NodeList = []
+    MacroPixelCoords = []
+
+    # initialized root
+    NodeList.append([0,0,np.shape(Input_image)[0], 0, 0,0,np.shape(Input_image)[0]])
+
+    while len(NodeList):
+
+        # create node's children
+        Children = NewLayer(NodeList[0], Input_image, evaluation_method = signal_eval_method)
+        NodeList.pop(0) # delete investigated node
+       
+        #check wether exit condition is met
+        if exit_method == 'voting':
+            # check how many of children are "bad"
+            flag_list = [np.int32(f[3]>= n_bad) for f in Children]
+            if np.sum(flag_list) > threshold*len(Children):
+                MacroPixelCoords.append(Children[0][4:]) # store parent node
+                Children = []
+        else:
+            # check if some or all children are "bad"
+            flag_list = [f[3]==n_bad for f in Children]
+            if all(flag_list): # if all children are "bad"
+                MacroPixelCoords.append(Children[0][4:]) # store parent node
+                Children = []
+            else:
+                Children = [ch for ch in Children if ch[3] != n_bad]
+
+        # check whether minimum dimension has been reached
+        l_list = [ch[2] == 1 for ch in Children]
+        idx = np.where(l_list)[0]
+        if len(idx):
+            for i in range(0, len(l_list)):
+                if l_list[i] == True:
+                    MacroPixelCoords.append(Children[i][0:3])
+            Children = [ch for ch in Children if ch[2] != 1]
+
+        NodeList.extend(Children)
+
+    return(MacroPixelCoords)
+
+
+def plot_masked_image(original_img, MacroPixelCoords):
+
+    NewImage = np.empty([np.shape(original_img)[0], np.shape(original_img)[0]])*np.nan
+    for macro in MacroPixelCoords:
+        # fill pixels belonging to the same macropixel with the same signal
+        mean_signal = np.nanmean(original_img[macro[0]:macro[0] + macro[2], macro[1]:macro[1]+macro[2]],
+                                 axis = (0,1))
+        NewImage[macro[0]:macro[0] + macro[2], macro[1]:macro[1] + macro[2]] = np.mean(mean_signal)
+
+    fig, axs = plt.subplots(1, 3)
+    fig.set_size_inches(6,2, forward=True)
+    im = axs[0].imshow(np.nanmean(original_img, axis = 2))
+    axs[0].set_xticks([])
+    axs[0].set_yticks([])
+    axs[0].set_title('Original image', fontsize = 7.)
+
+    im = axs[1].imshow(NewImage)
+    axs[1].set_xticks([])
+    axs[1].set_yticks([])
+    axs[1].set_title('Post sampling', fontsize = 7.)
+
+    ls = [macro[2] for macro in MacroPixelCoords]
+
+    im = axs[2].hist(ls, bins = np.max(ls))
+    axs[2].set_yscale('Log')
+    axs[2].set_xlabel('macro-pixel size', fontsize = 7.)
+
+    plt.tight_layout()
+    return axs
+
+if __name__ == '__main__':
+    CLI = argparse.ArgumentParser(description=__doc__,
+                   formatter_class=argparse.RawDescriptionHelpFormatter)
+    CLI.add_argument("--data",    nargs='?', type=str, required=True,
+                     help="path to input data in neo format")
+    CLI.add_argument("--output",  nargs='?', type=str, required=True,
+                     help="path of output file")
+    CLI.add_argument("--output_img",  nargs='?', type=none_or_str,
+                     help="path of output image", default=None)
+    CLI.add_argument("--n_bad_nodes",  nargs='?', type=none_or_int,
+                     help="number of non informative macro-pixel to prune branch", default=2)
+    CLI.add_argument("--exit_condition",  nargs='?', type=none_or_str,
+                     help="exit condition in the optimal macro-pixel dimension tree search", default='consecutive')
+    CLI.add_argument("--signal_eval_method",  nargs='?', type=none_or_str,
+                     help="signal to noise ratio evalutaion method", default='shapiro')
+    CLI.add_argument("--voting_threshold",  nargs='?', type=none_or_float,
+                     help="threshold of non informative nodes percentage if voting method is selected", default=0.5)
+    args = CLI.parse_args()
+
+    block = load_neo(args.data)
+    asig = block.segments[0].analogsignals[0]
+    block = analogsignals_to_imagesequences(block)
+    
+    # load image sequences at the original spatial resolution
+    imgseq = block.segments[0].imagesequences[-1]
+    imgseq_array = np.swapaxes(imgseq.as_array().T, 0, 1)
+    dim_x, dim_y, dim_t = imgseq_array.shape
+
+    # pad image sequences with nans to make it divisible by 2
+    N_pad = next_power_of_2(max(dim_x, dim_y)) 
+    padded_image_seq = np.pad(imgseq_array, 
+                         pad_width = [((N_pad-dim_x)//2,(N_pad-dim_x)//2 + (N_pad-dim_x)%2), 
+                                      ((N_pad-dim_y)//2, (N_pad-dim_y)//2 + (N_pad-dim_y)%2), 
+                                      (0,0)], mode = 'constant', constant_values = np.nan)
+    # tree search for the best macro-pixel dimension
+    # List con x,y,L,flag,x_parent, y_parent, L_parent
+    MacroPixelCoords = CreateMacroPixel(Input_image = padded_image_seq,
+                                        exit_method = args.exit_condition,
+                                        signal_eval_method = args.signal_eval_method,
+                                        threshold = args.voting_threshold,
+                                        n_bad = args.n_bad_nodes)
+    if args.output_img is not None:
+        plot_masked_image(padded_image_seq, MacroPixelCoords)
+        save_plot(args.output_img)
+
+    signal = np.empty([len(MacroPixelCoords), dim_t]) #save data as analogsignal
+    coordinates = np.empty([len(MacroPixelCoords), 3]) #pixel coordinates [x,y,L] to retrieve 
+                                                       # original one
+    ch_id = np.empty([len(MacroPixelCoords)]) # new channel id
+    x_coord = np.empty([len(MacroPixelCoords)]) # new x coord
+    y_coord = np.empty([len(MacroPixelCoords)]) # new y coord
+    x_coord_cm = np.empty([len(MacroPixelCoords)]) # new x coord
+    y_coord_cm = np.empty([len(MacroPixelCoords)]) # new y coord
+
+    for px_idx, px in enumerate(MacroPixelCoords): # for each new pixel
+        signal[px_idx, :] = np.nanmean(padded_image_seq[px[0]:px[0]+px[2], 
+                                                     px[1]:px[1]+px[2]], 
+                                    axis = (0,1))
+        x_coord_cm[px_idx], y_coord_cm[px_idx] = ComputeCenterOfMass(padded_image_seq[px[0]:px[0]+px[2], px[1]:px[1]+px[2]],
+                                 imgseq.spatial_scale)
+
+        coordinates[px_idx] = px
+        ch_id[px_idx] = px_idx
+        x_coord[px_idx] = (px[0] + px[2]/2.)*imgseq.spatial_scale
+        y_coord[px_idx] = (px[1] + px[2]/2.)*imgseq.spatial_scale
+
+    new_evt_ann = {'x_coords': coordinates.T[0],
+                   'y_coords': coordinates.T[1],
+                   'x_coord_cm': x_coord_cm,
+                   'y_coord_cm': y_coord_cm,
+                   'pixel_coordinates_L': coordinates.T[2],
+                   'channel_id': ch_id}
+
+
+    new_asig = asig.duplicate_with_new_data(signal.T)
+    #new_asig.array_annotations = asig.array_annotations
+    new_asig.array_annotations.update(new_evt_ann)
+    new_asig.name += ""
+    new_asig.description += "Non homogeneous downsampling obtained by cheching the signal to noise ratio of macropixels ad different size."
+    block.segments[0].analogsignals[0] = new_asig
+
+    write_neo(args.output, block)
+
+
+