Kittens are basically living, breathing, fuzzy cuteness. We love seeing their adorable eyes, and we love hearing their sweet little mews. But one day, you realize the fuzzy baby is no longer that little and you need two hands to hold it. How did that happen?

To find out Bored Panda talked to Molly DeVoss, a certified feline behaviorist who runs Cat Behavior Solutions, an agency with a vision to reduce the number of cats euthanized in shelters. Molly said that her cat passed last year and she got a new kitten in June of last year, so 10 months later he seems huge to her – and he still has growing to do!

“A one-year-old cat is equivalent to a 15-year old teenager. Cats reach their full adult size at about 18 months to two years of age, but can continue to grow up to four years of age.”

Meanwhile, “a cat reaches social maturity between two and four years and this is when behavioral problems may develop,” warned Molly and added that “Interact aggression is the most common, as mature cats begin to seek dominance.”

If you feel like your kitten is growing too fast, you’re not alone. Molly said that “it seems like time is flying by when you watch a kitten develop.”

“They will double in size in the first week and gain about an ounce every two-to-three days. A kitten's critical socialization period is between 2-7 weeks of age. In this short window of time, you want to expose your kittens to as many different stimuli as possible so they are not fearful of these things later in life.”

“By eight weeks the kitten should weigh enough to be spayed or neutered. Kittens will start to lose their baby teeth at about three months old and by the time they are 6-7 months of age, all 30 adult teeth will be in.”

And when it comes to a transformation, the biggest visible change you see in kittens is they grow into their heads. “Part of what makes them so cute is their big, round faces and eyes,” Molly said.

Moreover, “A kitten’s hyperactivity also starts to decrease at about eight months of age and usually by the time they are a year old they are seeking more cuddle time and less curtain climbing activities,” the cat behavior expert explained.