diff --git a/HISTORY.md b/HISTORY.md
index 3bafb6c5..e6b33afa 100755
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -46,6 +46,7 @@
 * threads: clear "answer" on ASK nothing/falsy
 * byob, blocks: export block definition from inside the block editor
 * objects: added "code" field to Costume constructor
+* objects, gui, extensions, store: support blocks embedded into costumes (under construction)
 
 ### 2022-04-19
 * threads: ASK nothing or a falsy value terminates the thread currently displaying a question
diff --git a/src/extensions.js b/src/extensions.js
index a983f698..e2445b63 100644
--- a/src/extensions.js
+++ b/src/extensions.js
@@ -29,11 +29,12 @@
 
 /*global modules, List, StageMorph, Costume, SpeechSynthesisUtterance, Sound,
 IDE_Morph, CamSnapshotDialogMorph, SoundRecorderDialogMorph, isSnapObject, nop,
-Color, Process, contains, localize, SnapTranslator, isString, detect*/
+Color, Process, contains, localize, SnapTranslator, isString, detect,
+SVG_Costume*/
 
 /*jshint esversion: 11, bitwise: false*/
 
-modules.extensions = '2022-April-07';
+modules.extensions = '2022-April-20';
 
 // Global stuff
 
@@ -668,6 +669,24 @@ SnapExtensions.primitives.set(
     }
 );
 
+// Costumes (cst_):
+
+SnapExtensions.primitives.set(
+    // experimental, will probably be taken out again, don't rely on this
+    'cst_code(cst, code)',
+    function (cst, code, proc) {
+        var ide = this.parentThatIsA(IDE_Morph);
+        proc.assertType(cst, 'costume');
+        proc.assertType(code, 'text');
+        if (cst instanceof SVG_Costume) {
+            throw new Error('option currently not supported for SVG costumes');
+        }
+        cst.code = code || null;
+        cst.version = Date.now();
+        ide.recordUnsavedChanges();
+    }
+);
+
 // Variables (var_):
 
 SnapExtensions.primitives.set(
diff --git a/src/gui.js b/src/gui.js
index 7a27b060..531d788a 100644
--- a/src/gui.js
+++ b/src/gui.js
@@ -86,7 +86,7 @@ BlockVisibilityDialogMorph, ThreadManager*/
 
 // Global stuff ////////////////////////////////////////////////////////
 
-modules.gui = '2022-April-06';
+modules.gui = '2022-April-20';
 
 // Declarations
 
@@ -9919,11 +9919,13 @@ CostumeIconMorph.prototype.init = function (aCostume) {
 };
 
 CostumeIconMorph.prototype.createThumbnail = function () {
-    var txt;
+    var watermark, txt;
     SpriteIconMorph.prototype.createThumbnail.call(this);
-    if (this.object instanceof SVG_Costume) {
+    watermark = this.object instanceof SVG_Costume ? 'svg'
+        : (this.object.code ? '</>' : null);
+    if (watermark) {
         txt = new StringMorph(
-            'svg',
+            watermark,
             this.fontSize * 0.8,
             this.fontStyle,
             false,
@@ -9970,6 +9972,9 @@ CostumeIconMorph.prototype.userMenu = function () {
     menu.addItem("duplicate", "duplicateCostume");
     menu.addItem("delete", "removeCostume");
     menu.addLine();
+    if (this.object.code) {
+        menu.addItem("get blocks", "importCode");
+    }
     menu.addItem("export", "exportCostume");
     return menu;
 };
@@ -10049,6 +10054,10 @@ CostumeIconMorph.prototype.removeCostume = function () {
     }
 };
 
+CostumeIconMorph.prototype.importCode = function () {
+    this.parentThatIsA(IDE_Morph).droppedText(this.object.code);
+};
+
 CostumeIconMorph.prototype.exportCostume = function () {
     var ide = this.parentThatIsA(IDE_Morph);
     if (this.object instanceof SVG_Costume) {
diff --git a/src/objects.js b/src/objects.js
index 03e30820..c5b03eb7 100644
--- a/src/objects.js
+++ b/src/objects.js
@@ -10414,7 +10414,7 @@ function Costume(canvas, name, rotationCenter, noFit, maxExtent) {
     if (!noFit) {this.shrinkToFit(maxExtent || this.maxExtent()); }
     this.name = name || null;
     this.rotationCenter = rotationCenter || this.center();
-    this.code = null;
+    this.code = null; // must be a string or null
     this.version = Date.now(); // for observer optimization
     this.loaded = null; // for de-serialization only
 }
diff --git a/src/store.js b/src/store.js
index a5f34d3c..36ccf3c7 100644
--- a/src/store.js
+++ b/src/store.js
@@ -63,7 +63,7 @@ Project*/
 
 // Global stuff ////////////////////////////////////////////////////////
 
-modules.store = '2022-April-05';
+modules.store = '2022-April-20';
 
 // XML_Serializer ///////////////////////////////////////////////////////
 /*
@@ -1651,6 +1651,12 @@ SnapSerializer.prototype.loadValue = function (model, object) {
                     context.drawImage(image, 0, 0);
                     v.contents = canvas;
                     v.version = +new Date();
+                    if (Object.prototype.hasOwnProperty.call(
+                        model.attributes,
+                        'code'
+                    )) {
+                        v.code = model.attributes.code;
+                    }
                     if (typeof v.loaded === 'function') {
                         v.loaded();
                     } else {
@@ -1977,12 +1983,13 @@ Costume.prototype[XML_Serializer.prototype.mediaDetectionProperty] = true;
 
 Costume.prototype.toXML = function (serializer) {
     return serializer.format(
-        '<costume name="@" center-x="@" center-y="@" image="@" ~/>',
+        '<costume name="@" center-x="@" center-y="@" image="@"% ~/>',
         this.name,
         this.rotationCenter.x,
         this.rotationCenter.y,
         this instanceof SVG_Costume ? this.contents.src
-                : normalizeCanvas(this.contents).toDataURL('image/png')
+                : normalizeCanvas(this.contents).toDataURL('image/png'),
+        this.code ? serializer.format(' code="@"', this.code) : ''
     );
 };