There are numerous photos hidden in certain levels of Cut the Rope: Experiments, which can be added to the Professor's Album. You can notice them by the peeling wallpaper on the background of the level. To find them, follow the instructions below:
Magnifying Glass: Level 1-14 - Look out for peeled wallpaper on the top left of the background. Tap it to add it to the Professor's Album.
Candy Beaker: Level 2-19 - Look for the peeling wallpaper above the second star in the background - tap it to add the photo.
HD Television: Level 3-15 - The wallpaper can be seen peeling in the top right-hand corner. (iPad only)
Books: Level 3-19 - The peeled wallpaper for this level is to the right of the background.
Computer Screen: No peeling wallpaper for this one! You have to 'Like' the Cut the Rope group on Facebook with the link found in the Professor's Album.
Unlock Sticky Steps
Simply collect 80 stars total to unlock the Sticky Steps set of levels. It's rather easy to get 80 stars from the Getting Started and Shooting the Candy levels (you can get 75 total stars just from Getting Started).