# Coming from DiffusionPipeline

If you are familiar with [DiffusionPipeline](/docs/diffusers/main/en/api/pipelines/overview#diffusers.DiffusionPipeline) and are working with a [ModularPipeline](/docs/diffusers/main/en/api/modular_diffusers/pipeline#diffusers.ModularPipeline) for the first time, a few things work differently. They are listed here so that you have them in mind before you go through the [quickstart](./quickstart).

- **Loading is lazy and flexible.** [from_pretrained()](/docs/diffusers/main/en/api/modular_diffusers/pipeline#diffusers.ModularPipeline.from_pretrained) builds the pipeline from the repository's `modular_model_index.json` without loading any weights. [load_components()](/docs/diffusers/main/en/api/modular_diffusers/pipeline#diffusers.ModularPipeline.load_components) then loads them, and it doesn't have to be all at once: by default it loads everything, but you can load only the components you name with `names`, or the set one workflow needs with `workflow`. [update_components()](/docs/diffusers/main/en/api/modular_diffusers/pipeline#diffusers.ModularPipeline.update_components) lets you reuse a component you already have, or one that differs from the repository's spec. See [Loading components](./modular_pipeline#loading-components) and [Updating components](./modular_pipeline#updating-components).
- **[ModularPipeline](/docs/diffusers/main/en/api/modular_diffusers/pipeline#diffusers.ModularPipeline) reads a different index, `modular_model_index.json`**, but it also works with a repository that only has a `model_index.json`, as long as the model has a modular pipeline. The reverse is not true: [DiffusionPipeline](/docs/diffusers/main/en/api/pipelines/overview#diffusers.DiffusionPipeline) and the `AutoPipeline` classes don't work with a repository that only has a `modular_model_index.json`.
- **A call returns the pipeline state**, which holds the intermediate values too (`prompt_embeds`, `latents`, ...). Ask for what you need with the `output` argument, `output="images"` or `output=["images", "latents"]`, or read an attribute of the state, as in the [quickstart](./quickstart#run-a-pipeline). See [States](./modular_diffusers_states).
- **Classifier-free guidance is supported in the `guider` component**, not a `guidance_scale` call argument: `pipe.update_components(guider=ClassifierFreeGuidance(guidance_scale=5.0))`. See the [guiders guide](../using-diffusers/guiders).
- **There is no `callback_on_step_end`**; however, you can insert a block into the denoising loop to use your existing callback functions. See [Modular pipelines](../using-diffusers/callback#modular-pipelines) in the callbacks guide.
- **The pipeline is a graph of blocks** that you can change (pop, insert, replace) before building it with [init_pipeline()](/docs/diffusers/main/en/api/modular_diffusers/pipeline_blocks#diffusers.ModularPipelineBlocks.init_pipeline); `pipe.blocks` returns a copy, so edit the blocks first. See [Compose new workflows](./quickstart#compose-new-workflows).
- **Offloading is handled by a [ComponentsManager](/docs/diffusers/main/en/api/modular_diffusers/pipeline_components#diffusers.ComponentsManager)**, which can serve several pipelines that share components. See the [ComponentsManager guide](./components_manager#offloading).