diff --git a/sources/01b-visualization.ipynb b/sources/01b-visualization.ipynb
index 778c000..8da4fc2 100644
--- a/sources/01b-visualization.ipynb
+++ b/sources/01b-visualization.ipynb
@@ -108,7 +108,10 @@
    "source": [
     "## Previewing Downloaded Files\n",
     "\n",
-    "There is a function that, given a resolution and the band name, returns the correct file paths to use with the `rasterio` library.\n",
+    "The largest share of the product size is made up by `*.jp2` files, which are raster images which contain geocoded spectral band information at a fixed resolution.\n",
+    "Data on each spectral band captured by the Sentinel-2 mission is distributed on a per-file basis, which is why most of these files contain data on a single channel only.\n",
+    "An exception is the included True-Color Image, which contains data in red, green and blue channels.\n",
+    "There is a function that, given a resolution and one or more spectral band name, returns the correct file paths.\n",
     "It contains code to deal with compressed or uncompressed products."
    ]
   },