Early AI models were single-purpose specialists — one model for images, a separate one for text, another for speech. Multimodal models process multiple types of input (and increasingly, output) within one unified architecture, and that unification is genuinely new, not just marketing framing.
How Different Modalities Become Comparable
The core trick is converting every input type into the same kind of representation — a sequence of tokens or embeddings the same underlying transformer architecture can process, regardless of whether they originally came from text, image patches, or audio spectrograms:
Text: "a red car" -> tokenized into word/subword tokens Image: [pixel data] -> split into patches, each patch embedded as a token Audio: [waveform] -> converted to spectrogram, chunked into tokens All three token streams get processed by the same transformer architecture, attending across modalities -- letting the model relate "red" (text) to actual red pixels (image) within a single unified representation.
Practical Uses Already Here
- Image understanding — describing images, answering questions about a photo, reading text within an image (screenshots, documents, whiteboards)
- Voice conversations — real-time speech in, speech out, without separate speech-to-text and text-to-speech pipelines bolted together
- Document understanding — processing a PDF’s layout, tables, and images together rather than just extracting raw text
A Simple Example: Asking About an Image
from openai import OpenAI
client = OpenAI()
response = client.chat.completions.create(
model="gpt-4o",
messages=[{
"role": "user",
"content": [
{"type": "text", "text": "What's unusual about this image?"},
{"type": "image_url", "image_url": {"url": "https://example.com/photo.jpg"}}
]
}]
)
print(response.choices[0].message.content)
Why This Matters Beyond Novelty
A single unified model reasoning jointly across modalities can catch relationships a pipeline of separate specialist models would miss entirely — connecting what’s said in a video’s audio to what’s simultaneously shown on screen, for instance — which is exactly the kind of cross-modal reasoning that stitched-together pipelines have always struggled with.