.I trying to go deeper in Smalltalk/Squeak

So I try to know which other classes are needed for aClass and sure
reinvented something what is buried in image and yet don't found.

For #Morph, I get the following

 a Set(#Beeper #ByteArray #MenuMorph #CardPlayer #Object #SqueakPageCache
#UnscriptedCardPlayer #MorphThumbnail #MorphicEventDispatcher #Cursor
#BorderStyle #FileStream #URLMorph #PhraseTileMorph #SampledSound #Point
#ListViewLine #GradientFillStyle #TableLayout #IdentityDictionary
#CustomMenu #CollapsedMorph #GIFReadWriter #StringHolder #Browser #Flaps
#DescriptionForPartsBin #SketchMorph #ButtonProperties #String
#StandardViewer #FillInTheBlank #Utilities #MouseEvent #InfiniteForm
#MorphExtension #SketchEditorMorph #TrashCanMorph #IdentityTransform
#TextMorph #SystemWindow #PopUpMenu #Delay #ButtonPropertiesMorph
#SimpleServiceEntry #TwoWayScrollPane #Viewer #TextStyle #MorphWorldView
#Component #KeyboardEvent #SmallInteger #TextPlusPasteUpMorph
#DSCPostscriptCanvas #IconicButton #FileList #AlignmentMorph
#UnscriptedPlayer #SelectionMenu #MessageSet #ImageMorph #Rectangle
#CRDisplayProperties #SortedCollection #ObjectPropertiesMorph #Time
#MethodReference #DocLibrary #Project #TableLayoutProperties
#ProportionalLayout #TextPropertiesMorph #Color #SqueakPage #HandleMorph
#StackMorph #WarpBlt #Command #BitmapFillStyle #Preferences
#ColorPatchCanvas #PasteUpMorph #StringMorph #Bitmap #ColorForm
#FileDirectory #HaloMorph #LayoutProperties #Vocabulary #Inspector
#CRDictionary #MouseButtonEvent #BookMorph #SimpleButtonMorph
#ProgressTargetRequestNotification #EPSCanvas #CornerRounder
#MVCWiWPasteUpMorph #Error #AmbientEvent #MovieMorph #HandMorph
#TransformationMorph #Compiler #PostscriptCanvas #GraphicalMenu #IdentitySet
#ColorPickerMorph #EventHandler #Form #RealEstateAgent #ActorState
#Clipboard #WriteStream #PrintSpecifications #Imports #ServerDirectory
#Character #OrderedCollection #CommandHistory #ReadStream #BalloonMorph
#ScriptEditorMorph #Array #MethodInterface #SyntaxMorph #Model)


So my question is , why we get classes what could need other classes below
in hierarchy (Chicken and egg problem)?

Where in web I could find material for study?

Thanks in advance.
Edgar