public static IntFunction<Inventory> Guide(List<Category> categories, Plugin plugin, int rows) {
	final MiniWindow window = new MiniWindow(plugin);
	final List<Supplier<Inventory>> pages = new ArrayList<>();
	final List<List<Category>> partitions = partition(categories, rows * 9);
	pages.addAll(mapWithIndex(partitions.stream(), (categoryList, index) ->
			cache(() -> window.page(page -> {
				//Title the page.
				page.title("Page " + index);

				//Add items for each category on the page.
				categoryList.forEach(category -> {
					//Create a new item for the category.
					Item item = page.element();

					//Let the category style it.
					category.itemLike().accept(item);

					//Cache the category's page as well.
					Supplier<Inventory> categoryPage = cache(() ->
							window.page(category.pageLike())
					);

					//Open the category's page when it's icon is clicked.
					item.onClick(player ->
							player.openInventory(categoryPage.get())
					);
				});

				//Footer time.
				for (int i = 0; i < 9; i++) {
					Item item = page.element(rows + 1).icon(STAINED_GLASS_PANE);
					if (index != 0 && i == 2)
						item.data(RED.getDyeData()).onClick(player ->
								//Navigate back one page.
								player.openInventory(pages.get((int) (index - 1)).get())
						);
					else if (index != partitions.size() - 1 && i == 6)
						item.data(GREEN.getDyeData()).onClick(player ->
								//Navigate forward one page.
								player.openInventory(pages.get((int) (index + 1)).get())
						);
					else
						item.data(GRAY.getDyeData());
				}
			}))
	).collect(toList()));

	return index -> pages.get(index).get();
}