A modern diffusion model, like [Stable Diffusion XL (SDXL)](../using-diffusers/sdxl), is not just a single model, but a collection of multiple models. SDXL has four different model-level components:  
* A variational autoencoder (VAE)
* Two text encoders
* A UNet for denoising  
Usually, the text encoders and the denoiser are much larger compared to the VAE.