I started by modeling some flowers in virtual reality (VR) in an application called Anyland. I then exported these files and uploaded them into the HoloLens where I was able to place the holograms into physical space. I placed these flowers outside on the street and am very interested in the contrast between my fake flowers and the reality of the surrounding world. 
Below is another experiment using the HoloLens. This time I went to my local park and placed a 3D model I made of a fern leave into the grass. I like the how subtly the virtual leave blends into nature and it becomes hard to tell what is real and what is fake. The other video is of a 3D animated model of a butterfly I made, flying around the park, again using the the HoloLens.
In this video at the beginning you can see me using the spatial mapping feature of the HoloLens. Spatial mapping provides a detailed representation of real-world surfaces in the environment around the HoloLens, which is very exciting and will allow me to create a very convincing mixed reality experience. By merging the real world with the virtual world the holograms seem to appear real, also by providing familiar real-world behaviors and interactions.