diff --git a/docs/dev_logs/2025_May.md b/docs/dev_logs/2025_May.md
index eb52903..57859b3 100644
--- a/docs/dev_logs/2025_May.md
+++ b/docs/dev_logs/2025_May.md
@@ -16,8 +16,10 @@
 - [ ] Add Simon's example
 
 ### Doing:
-- [ ] Compressing code
-- [ ] GemPy posterior visualization
+- [x] Compressing code
+- [x] GemPy posterior visualization
+- [ ] Add proper thickness likelihood
+- [ ] Speed
 
 ### Possible Design:
 - Geological Model
diff --git a/gempy_probability/modules/likelihoods/__init__.py b/gempy_probability/modules/likelihoods/__init__.py
new file mode 100644
index 0000000..e88d21a
--- /dev/null
+++ b/gempy_probability/modules/likelihoods/__init__.py
@@ -0,0 +1,3 @@
+from ._apparent_thickness import apparent_thickness_likelihood, apparent_thickness_likelihood_II
+from ._gravity_inv import gravity_inversion_likelihood
+
diff --git a/gempy_probability/modules/likelihoods/_apparent_thickness.py b/gempy_probability/modules/likelihoods/_apparent_thickness.py
new file mode 100644
index 0000000..40c6950
--- /dev/null
+++ b/gempy_probability/modules/likelihoods/_apparent_thickness.py
@@ -0,0 +1,28 @@
+import gempy as gp
+import torch
+import pyro
+
+def apparent_thickness_likelihood(model_solutions: gp.data.Solutions) -> torch.Tensor:
+    """
+    This function computes the thickness of the geological layer.
+    
+    Notes: This is not completed
+    """
+    simulated_well = model_solutions.octrees_output[0].last_output_center.custom_grid_values
+    thickness = simulated_well.sum()
+    pyro.deterministic(
+        name=r'$\mu_{thickness}$',
+        value=thickness.detach()  # * This is only for az to track progress
+    )
+    return thickness
+
+def apparent_thickness_likelihood_II(model_solutions: gp.data.Solutions, distance: float, element_lith_id: float) -> torch.Tensor:
+    # TODO: element_lith_id should be an structured element  
+    simulated_well = model_solutions.octrees_output[0].last_output_center.custom_grid_values
+
+    # Create a boolean mask for all values between element_lith_id and element_lith_id+1
+    mask = (simulated_well >= element_lith_id) & (simulated_well < (element_lith_id + 1))
+
+    # Count these values and compute thickness as the product of the count and the distance
+    thickness = mask.sum() * distance
+    return thickness
diff --git a/gempy_probability/modules/likelihoods/_gravity_inv.py b/gempy_probability/modules/likelihoods/_gravity_inv.py
new file mode 100644
index 0000000..889af2d
--- /dev/null
+++ b/gempy_probability/modules/likelihoods/_gravity_inv.py
@@ -0,0 +1,9 @@
+import pyro
+import torch
+import gempy as gp
+
+def gravity_inversion_likelihood(model_solutions: gp.data.Solutions) -> torch.Tensor:
+    simulated_geophysics = model_solutions.gravity
+    pyro.deterministic(r'$\mu_{gravity}$', simulated_geophysics)
+    
+    return simulated_geophysics
\ No newline at end of file
diff --git a/gempy_probability/modules/model_definition/model_examples.py b/gempy_probability/modules/model_definition/model_examples.py
index 5765d86..fc8aeea 100644
--- a/gempy_probability/modules/model_definition/model_examples.py
+++ b/gempy_probability/modules/model_definition/model_examples.py
@@ -2,6 +2,7 @@
 import gempy.core.data
 import gempy_engine
 from gempy.modules.data_manipulation.engine_factory import interpolation_input_from_structural_frame
+from gempy_probability.modules.likelihoods import apparent_thickness_likelihood
 
 import pyro
 import pyro.distributions as dist
@@ -53,7 +54,7 @@ def model(geo_model: gempy.core.data.GeoModel, normal, y_obs_list):
 
     # Compute and observe the thickness of the geological layer
     model_solutions: gp.data.Solutions = geo_model.solutions
-    thickness = _likelihood(model_solutions)
+    thickness = apparent_thickness_likelihood(model_solutions)
 
     # endregion
 
@@ -67,14 +68,3 @@ def model(geo_model: gempy.core.data.GeoModel, normal, y_obs_list):
     )
 
 
-def _likelihood(model_solutions: gp.data.Solutions) -> torch.Tensor:
-    """
-    This function computes the thickness of the geological layer.
-    """
-    simulated_well = model_solutions.octrees_output[0].last_output_center.custom_grid_values
-    thickness = simulated_well.sum()
-    pyro.deterministic(
-        name=r'$\mu_{thickness}$',
-        value=thickness.detach()  # * This is only for az to track progress
-    )
-    return thickness
diff --git a/tests/test_likelihoods/__init__.py b/tests/test_likelihoods/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_likelihoods/test_geometric_likelihoods.py b/tests/test_likelihoods/test_geometric_likelihoods.py
new file mode 100644
index 0000000..d6ee9ab
--- /dev/null
+++ b/tests/test_likelihoods/test_geometric_likelihoods.py
@@ -0,0 +1,98 @@
+import numpy as np
+import os
+
+import gempy as gp
+import gempy_viewer as gpv
+from gempy.core.data.grid_modules import CustomGrid
+from gempy_engine.core.backend_tensor import BackendTensor
+from gempy_probability.modules.likelihoods import apparent_thickness_likelihood_II
+
+
+def test_gempy_posterior_I():
+    current_dir = os.path.dirname(os.path.abspath(__file__))
+    data_path = os.path.abspath(os.path.join(current_dir, '..', '..', 'examples', 'tutorials', 'data'))
+    geo_model = gp.create_geomodel(
+        project_name='Wells',
+        extent=[0, 12000, -500, 500, 0, 4000],
+        refinement=4,
+        importer_helper=gp.data.ImporterHelper(
+            path_to_orientations=os.path.join(data_path, "2-layers", "2-layers_orientations.csv"),
+            path_to_surface_points=os.path.join(data_path, "2-layers", "2-layers_surface_points.csv")
+        )
+    )
+
+    BackendTensor.change_backend_gempy(engine_backend=gp.data.AvailableBackends.PYTORCH)
+
+    geo_model.interpolation_options.uni_degree = 0
+    geo_model.interpolation_options.mesh_extraction = False
+
+    x_loc = 6000
+    y_loc = 0
+    z_loc = np.linspace(0, 4000, 100)
+    dz = (4000 - 0)/100
+    xyz_coord = np.array([[x_loc, y_loc, z] for z in z_loc])
+
+    custom_grid = CustomGrid(xyz_coord)
+    geo_model.grid.custom_grid = custom_grid
+    gp.set_active_grid(
+        grid=geo_model.grid,
+        grid_type=[gp.data.Grid.GridTypes.CUSTOM]
+    )
+    gp.compute_model(gempy_model=geo_model)
+    p2d = gpv.plot_2d(
+        model=geo_model,
+        show_topography=False,
+        legend=False,
+        show_lith=False,
+        show=False
+    )
+    
+    element_lith_id = 1.5
+    thickness = apparent_thickness_likelihood_II(
+        model_solutions=geo_model.solutions,
+        distance=dz,
+        element_lith_id=element_lith_id
+    )
+    
+    print(thickness)
+
+    p2d = gpv.plot_2d(geo_model, show_topography=False, legend=False, show=False)
+    # --- New code: plot all custom grid points with lithology 1 ---
+    #
+    # Extract the simulated well values from the solution obtained.
+    simulated_well = geo_model.solutions.octrees_output[0].last_output_center.custom_grid_values
+    #
+    # Create a boolean mask for all grid points whose value is between 1 and 2.
+    mask = (simulated_well >= element_lith_id) & (simulated_well < (element_lith_id + 1))
+    #
+    # Retrieve the custom grid coordinates.
+    grid_coords = geo_model.grid.custom_grid.values
+    #
+    # Use the mask to get only the grid points corresponding to lith id 1.
+    # Note: Convert the boolean mask to a NumPy array if necessary.
+    coords_lith1 = grid_coords[mask]
+    #
+    # Plot these points on the figure (using the x and z columns for a 2D image).
+    p2d.axes[0].scatter(
+        coords_lith1[:, 0],
+        coords_lith1[:, 2],
+        marker='o',
+        s=80,
+        c='green',
+        label='Lith id = 1',
+        zorder=9
+    )
+    p2d.axes[0].legend()
+    # --------------------------------------------------------------
+
+    # Plot device location for reference.
+    device_loc = np.array([[6e3, 0, 3700]])
+    p2d.axes[0].scatter(
+        device_loc[:, 0],
+        device_loc[:, 2],
+        marker='x',
+        s=400,
+        c='#DA8886',
+        zorder=10
+    )
+    p2d.fig.show()
diff --git a/tests/test_posterior_analysis/test_gempy_posterior_I.py b/tests/test_posterior_analysis/test_gempy_posterior_I.py
index 09e3a31..958b800 100644
--- a/tests/test_posterior_analysis/test_gempy_posterior_I.py
+++ b/tests/test_posterior_analysis/test_gempy_posterior_I.py
@@ -22,7 +22,7 @@ def test_gempy_posterior_I():
             path_to_surface_points=os.path.join(data_path, "2-layers", "2-layers_surface_points.csv")
         )
     )
-    
+
     BackendTensor.change_backend_gempy(engine_backend=gp.data.AvailableBackends.PYTORCH)
 
     geo_model.interpolation_options.uni_degree = 0
@@ -47,7 +47,7 @@ def test_gempy_posterior_I():
     xyz[:, 2] = posterior_top_mean_z
     world_coord = geo_model.input_transform.apply_inverse(xyz)
     i = 0
-    for i in range(0, 200, 5):
+    for i in np.linspace(0, 200, 20).astype(int):
         gp.modify_surface_points(
             geo_model=geo_model,
             slice=0,
@@ -72,8 +72,6 @@ def test_gempy_posterior_I():
 
     p2d.fig.show()
 
-    pass
-
 
 def _plot_posterior(data):
     az.plot_trace(data)