diff --git a/src/cellmap_data/dataloader.py b/src/cellmap_data/dataloader.py
index 2a8f944..1c49441 100644
--- a/src/cellmap_data/dataloader.py
+++ b/src/cellmap_data/dataloader.py
@@ -1,6 +1,4 @@
 from torch.utils.data import DataLoader
-from torch.utils.data.dataloader import _BaseDataLoaderIter
-from .dataset import CellMapDataset
 from .datasplit import CellMapDataSplit
 from typing import Callable, Iterable
 
@@ -17,25 +15,3 @@ class CellMapDataLoader(DataLoader):
     is_train: bool
     augmentations: list[dict[str, any]]
     to_target: Callable
-
-    def __init__(
-            ...)
-    
-    def __getitem__(self, idx: int) -> dict[str, tuple[torch.Tensor, torch.Tensor]]:
-        """Returns the input and target data for the given index."""
-        ...
-    
-    def __len__(self) -> int:
-        """Returns the length of the dataset."""
-        ...
-
-    def __iter__(self):
-        
-    
-    def _apply_augmentations(self, data: dict[str, torch.Tensor]) -> dict[str, torch.Tensor]:
-        """Applies augmentations to the data."""
-        ...
-
-    def _to_target(self, data: dict[str, torch.Tensor]) -> dict[str, torch.Tensor]:
-        """Converts the input data to the target data."""
-        ...
diff --git a/src/cellmap_data/dataset.py b/src/cellmap_data/dataset.py
index b3ff157..5ece7e5 100644
--- a/src/cellmap_data/dataset.py
+++ b/src/cellmap_data/dataset.py
@@ -1,10 +1,20 @@
 # %%
 import csv
 from typing import Callable, Dict, Iterable, Optional
+import torch
 from torch.utils.data import Dataset
 import tensorstore as tswift
 from fibsem_tools.io.core import read, read_xarray
-from .image import CellMapImage
+from .image import CellMapImage, EmptyImage
+
+
+def split_gt_path(path: str) -> tuple[str, list[str]]:
+    """Splits a path to groundtruth data into the main path string, and the classes supplied for it."""
+    path_prefix, path_rem = path.split("[")
+    classes, path_suffix = path_rem.split("]")
+    classes = classes.split(",")
+    path_string = path_prefix + "{label}" + path_suffix
+    return path_string, classes
 
 
 # %%
@@ -17,7 +27,7 @@ class CellMapDataset(Dataset):
     input_arrays: dict[str, dict[str, Iterable[int | float]]]
     target_arrays: dict[str, dict[str, Iterable[int | float]]]
     input_sources: dict[str, CellMapImage]
-    target_sources: dict[str, dict[str, CellMapImage]]
+    target_sources: dict[str, dict[str, CellMapImage | EmptyImage]]
 
     def __init__(
         self,
@@ -51,7 +61,8 @@ def __init__(
                 }
         """
         self.raw_path = raw_path
-        self.gt_path = gt_path
+        self.gt_paths = gt_path
+        self.gt_path_str, self.classes_with_path = split_gt_path(gt_path)
         self.classes = classes
         self.input_arrays = input_arrays
         self.target_arrays = target_arrays
@@ -65,7 +76,9 @@ def __getitem__(self, idx):
         """Returns a random crop of the input and target data as PyTorch tensors."""
         ...
 
-    def __iter__(self): ...
+    def __iter__(self):
+        """Iterates over the dataset, covering each section of the bounding box. For instance, for calculating validation scores."""
+        ...
 
     def construct(self):
         """Constructs the input and target sources for the dataset."""
@@ -78,15 +91,22 @@ def construct(self):
                 array_info["shape"],
             )
         self.target_sources = {}
+        self.has_data = False
         for array_name, array_info in self.target_arrays.items():
             self.target_sources[array_name] = {}
             for label in self.classes:
-                self.target_sources[array_name][label] = CellMapImage(
-                    self.gt_path,
-                    label,
-                    array_info["scale"],
-                    array_info["shape"],
-                )
+                if label in self.classes_with_path:
+                    self.target_sources[array_name][label] = CellMapImage(
+                        self.gt_path_str.format(label=label),
+                        label,
+                        array_info["scale"],
+                        array_info["shape"],
+                    )
+                    self.has_data = True
+                else:
+                    self.target_sources[array_name][label] = EmptyImage(
+                        label, array_info["shape"]
+                    )
 
     @property
     def bounding_box(self):
@@ -94,6 +114,8 @@ def bounding_box(self):
         if self._bounding_box is None:
             bounding_box = {c: [0, 2**32] for c in "xyz"}
             for source in [self.input_sources.values(), self.target_sources.values()]:
+                if source.bounding_box is None:
+                    continue
                 for c, (start, stop) in source.bounding_box.items():
                     bounding_box[c][0] = max(bounding_box[c][0], start)
                     bounding_box[c][1] = min(bounding_box[c][1], stop)
diff --git a/src/cellmap_data/image.py b/src/cellmap_data/image.py
index 8ded8d0..577dad4 100644
--- a/src/cellmap_data/image.py
+++ b/src/cellmap_data/image.py
@@ -52,3 +52,35 @@ def class_counts(self) -> int:
             # TODO
             ...
         return self._class_counts
+
+
+class EmptyImage:
+    shape: tuple[float, ...]
+    label_class: str
+    class_count: int
+    store: torch.Tensor
+
+    def __init__(
+        self,
+        target_class: str,
+        target_voxel_shape: Iterable[int],
+    ):
+        self.label_class = target_class
+        self.output_shape = tuple(target_voxel_shape)
+        self._bounding_box = None
+        self._class_counts = 0
+        self.store = torch.zeros(self.output_shape)
+
+    def __getitem__(self, center: Iterable[float]):
+        """Returns image data centered around the given point, based on the scale and shape of the target output image."""
+        return self.store
+
+    @property
+    def bounding_box(self) -> None:
+        """Returns the bounding box of the dataset."""
+        return self._bounding_box
+
+    @property
+    def class_counts(self) -> int:
+        """Returns the number of pixels for the contained class in the ground truth data, normalized by the resolution."""
+        return self._class_counts