[Django]-How to show related objects in Django/Admin?

You can use “Inlines” to visualize and edit Things of a certain Category in the admin detail for that category:

In the admin.py file, create an Inline object for Thing (ThingInline) and modify your CategoryAdmin class to have an inline of type ThingInline like this:

...
class ThingInline(admin.TabularInline):
    model = Thing

class CategoryAdmin(admin.ModelAdmin):
    inlines = [
        ThingInline,
    ]
...

For further details, this is the docs for admin inlines: https://docs.djangoproject.com/en/dev/ref/contrib/admin/#inlinemodeladmin-objects

update admin.py file like this.

from django.contrib import admin
from .views import Category, Thing

class CategoryAdmin(admin.ModelAdmin):
    inlines = [
        ThingInline,
    ]

class ThingInline(admin.TabularInline):
    model = Thing

admin.site.register(Category, CategoryAdmin) 
admin.site.register(Thing)

There are two inline options TabularInline and StackedInline

Few minutes ago, searching how to solve a similar problem, I finally found a solution.

You actually have to follow @Matteo Scotuzzi answer as well, then

Inside admin.py located in the app your created those models, you have to declare as follows right bellow @Matteo snippet:

admin.site.register(Category, CategoryAdmin)

and that would be enough to make all "Things" appear in "Category" inside your Django Administration respective page which is "Category".