Hiding hair extensions in very short hair can be challenging, but it is not impossible. There are several techniques you can use to blend your hair extensions with your natural hair and create a seamless, natural-looking style.

1. Choose hair extensions that match your hair color and texture. The key to making your hair extensions look natural is to match them as closely as possible to your natural hair. Choose hair extensions that are the same color and texture as your natural hair, and avoid using extensions that are too long or thick.

2. Use a professional stylist. If you are not experienced in applying hair extensions, it is best to have them applied by a professional stylist. A stylist will be able to carefully blend the hair extensions with your natural hair and create a seamless, natural-looking style.

3. Use a hairpiece or topper. Another option is to use a hairpiece or topper, which is a small piece of hair that is attached to the top of your head to add volume and length. This can be a good option for very short hair, as it allows you to add length and volume without attaching the extensions directly to your natural hair.

4. Use micro-ring or tape-in extensions. If you have very short hair, you may want to consider using micro-ring or tape-in extensions. These types of extensions are applied using small rings or strips of tape, and can be a more gentle option for short hair.

5. Use a hair clip or headband. Finally, you can use a hair clip or headband to help hide your hair extensions and blend them with your natural hair. A hair clip or headband can be a quick and easy way to add length and volume to your hair, and can be removed easily when you want to take out the extensions.

In summary, hiding hair extensions in very short hair can be challenging, but it is not impossible. Choose hair extensions that match your hair color and texture, use a professional stylist, and consider using a hairpiece, micro-ring or tape-in extensions, or a hair clip or headband to help blend the extensions with your natural hair. With the right techniques, you can create a seamless, natural-looking style.