Here is a list of all achievements and how to get them.
I divided them into categories:

• Casual (Easiest achievements, you can get them just by playing, without further explanation)
  
• Intermediate (You need to try harder to get them)
  
• Advanced (These ones are related to secrets, collectibles)

With some time in your hand, you can get all of them without any problems.
If you need to find a specific achievement, use ctrl+f.

Thank you! <3
A thanks from developer for playing Size Matters!

Run the game, it will unlock.

So many choices!
Spend more than 1 minute in the play menu!

Just wait it out in the menu.

Aspiring Chemist!
Use Chemical Processor successfully for the first time ever!

Just use it, you can get it while playing the tutorial.

****
Enter a correct code into the Code Combiner!

Just use it correctly, you can get it while playing the tutorial.

The Restorer
Successfully use the Restorer!

Break a flask and use it. You need to turn on breakable flasks to be able to use the Restorer.

Uhmm, okay?
You mixed the wrong ingredients, luckily nothing blew up!

Take two random ingredients and mix them.

Baby Chemist
Complete a round on beginner difficulty! Baby Steps!

Select and finish beginner preset.

Beginner Chemist
Complete a round on normal difficulty

Select and finish normal preset.

Proficient Chemist
Complete a round on hard difficulty!

Select and finish hard preset.

Professional Chemist
Complete a round on crazy difficulty!

Select and finish crazy preset.

Gravity... It always seems to let us down
Complete a round on "Low Gravity" mode!

Select and finish low gravity preset.

Tiny Chemist!
Complete a round on "Tiny" mode

Select and finish tiny preset.

I don't need that!
Save yourself without having to use the Reverter!

Finish a level without using the Reverter.

Open the door!
Open drawers and cabinets more than 100 times!

You can view how many you opened in stats.

Professional Drawer Opener
Open drawers and cabinets more than 1000 times!

You can view how many you opened in stats.

Chemical Processor Expert!
Use Chemical Processor for more than 10 minutes!

Chemical Processor is used for mixing ingredients.

Chemical Reverter Expert!
Use Chemical Reverter for more than 10 minutes!

Chemical Reverter is used for reverting wrongly mixed ingredient.

Code Combiner Expert!
Use Code Combiner for more than 10 minutes!

Code Combiner is used to mix an ingredient with a code.

Microwave Expert!
Use Microwave for more than 10 minutes!

Microwave is used for microwaving an ingredient.

Restorer Expert!
Use Restorer for more than 10 minutes!

Restorer is used for fixing a broken ingredient. You need to turn on breakable flasks to be able to use the Restorer.

Whoops...
Shrink until you're too small!

Fail a level, wait until the timer ends.

True Winner
Win 10 or more rounds!

The preset doesn't matter.

True Expert
Win at least one round on all available laboratories!

You can change the laboratory in custom mode.

Whoa, that was close!
You saved yourself in the last minute!

Finish a level while having less than one minute left.

Ingredient hunter!
Find all ingredients in 30 seconds or faster!

You can do it without a problem on easy preset.

That's so sweet!
Consume one cupcake!

Pick it up and press E to eat it. You need to turn on the cupcakes to be able to find them.

Croissant!
Enlarge 3 or more objects in a single round!

Eat three croissants, take 3 objects and press E while holding them to enlarge. You need to turn on the croissants to be able to find them.

Not giving up on mistakes!
Win the round when you have reverted 5 or more ingredients!

Set the lowest reverter processing time, revert 5 times and finish the level.

You airplane now
Spend more than 5 seconds in air without touching ground

You can do it without a problem on low gravity preset.

No Object - No Problem
Win a round without picking up any object other than ingredients

The easiest way to do it is on easy preset, you can touch ingredients and clipboards.

Uhhh... what are you looking for?
Open the same drawer 10 times!

Just spam F on a drawer.

I AM SPEED
Win a round in under 7 minutes!

What the achievement says.

Klutz
Maybe try being a bit more careful? :(

Break a flask, if it doesn't work, keep breaking them. You need to turn on breakable flasks to be able to break them.

Snooping around?
Open all drawers in the laboratory at least once!

Start a level in lab 1, and open every drawer.

Must. Not. Jump.
Finish the level without jumping!

You have to be pretty fast for this one.

Is the floor dirty?
Finish the level without formulas and ingredients touching the floor!

It's easier than it sounds.

Do you even shrink?
Finish the level with 1.5 meters height left or more!

In custom mode, set your starting height and end height to max, choose shrink curve number 9 and you should be good.

The Lab Equipment Needs An Upgrade!
Finish the level with all "Processing Time" sliders to the max!

You can set this in custom mode, remember to set your mission time to a lot too.

You stink!
Take a shower!

Hint: Where can you touch the water?
Solution: Get into the sink, run the water.

Kill the Big Brother!
(x_x)

Hint: Lab 1, he's watching...
Solution: Throw anything at the camera in Lab 1.

I Thirst!
Have 10 concurrent water flasks!

Solution: Spam water bottles.

So fast! Whoa
When breakable flasks are enabled, break at least one at very high speed!

Hint: You can also break flasks by throwing them with right click.
Solution: Be tall, set your strength to max, take a flask and throw it across the room. You need to turn on breakable flasks to be able to break them.

Cracked Television!
Destroy the TV in Laboratory 3!

Solution: Be tall, throw anything at the TV in Lab 3.

Spooky Scary Skeletons
Check out the HUMAN SKELETON!

Hint: Lab 3.
Solution: In Lab 3, look at the human skeleton poster, it should activate after 5-10 seconds.

Find Love!
Find love in the kitchen!

Hint: This might be literal LOVE.
Solution: Pick up the love sign in Lab 4, near the TV and speaker set.

Pickups Laboratory 1!
Find all pickups in Laboratory 1!

Find and touch all 3 blue orbs in Lab 1.
Solutions:

• Orb 1: Under the cupboard, next to the sink
  
• Orb 2: Behind the desk where the microwave stands
  
• Orb 3: Under the camera, behind the cardboard box

Pickups Laboratory 2!
Find all pickups in Laboratory 2!

Find and touch all 3 blue orbs in Lab 2.
Solutions:

• Orb 1: On the shelf above the first aid kit
  
• Orb 2: Lower shelf of the cupboard, first doors next to the table that's under the painting of a sow
  
• Orb 3: Under the purple desk

Pickups Laboratory 3!
Find all pickups in Laboratory 3!

Find and touch all 3 blue orbs in Lab 3.
Solutions:

• Orb 1: In the second room, on the metal lockers
  
• Orb 2: In the first room, on the tall cupboard, next to the column with the fire alarm switch
  
• Orb 3: In the first room, in the moving desk under the paintings, there is a small gap where the cleaning products are.

Pickups Laboratory 4!
Find all pickups in Laboratory 4!

Find and touch all 3 blue orbs in Lab 4.
Solutions:

• Orb 1: Left doors, on the cupboard where the TV stands
  
• Orb 2: Under the table
  
• Orb 3: In the cupboard, under the sink

Pickups Laboratory 5!
Find all pickups in Laboratory 5!

Find and touch all 3 blue orbs in Lab 5.
Solutions:

• Orb 1: In the center of the room, between the moving desks
  
• Orb 2: Close to the first orb, there is a small glass door thing, it's inside
  
• Orb 3: On the top of the upper cupboards, there are two monitors under them

Pickups Laboratory 6!
Find all pickups in Laboratory 6!

Find and touch all 3 blue orbs in Lab 6.
Solutions:

• Orb 1: In the center of the room, between the double desk table
  
• Orb 2: Under the microwave, next to the red tool rack
  
• Orb 3: There is a small gap in the corner of the room, where the big closet is. It's there, on the ground

Pickups Pro!
Find ALL pickups in ALL laboratories!

It will unlock automatically after getting the previous 6 pickup achievements.

Breaker of Plates and Mugs!
Break all plates and mugs in the Kitchen!

Solution: You need to break all plates, mugs, cups and bowls on the entire Lab 4.

Spring Cleaning!
Empty out the fridge!

Hint: Tiny or custom preset.
Solution: Get everything out of the fridge in Lab 4.

Alien Encounters
Find an alien creature!

Hint 1: It's in Lab 6.
Hint 2: It's on the ground.
Solution: In Lab 6, you need to be less than 10cm (4 inches) tall, look under the red tool racks.

PLASTIC GREEN BIN
Get inside the green plastic bin!

Hint: Lab 3.
Solution: In Lab 3, go to the second room and get inside the green bin.

Not Good For Your Health
Get hit by ~microwaves~!

Hint 1: Yes, you need to do something with the microwave.
Hint 2: Maybe you need to use something else as well?
Solution: The microwave door opens when you want to put an ingredient into it. You can use that to enter the microwave, do that while being smaller than 20cm (8 inches). Then interact with the microwave again to close the door.